title: Invalid cast exception is raised when insert is performed into column of type SYSTIMESTAMP WITH TIME ZONE with default value
body: <p>Could you please assist with next: 
  I have a table with column of type SYSTIMESTAMP WITH TIME ZONE and with default value - SYSTIMESTAMP. I use Entity Framework 5 database first. When I try to insert entity in this table I get an exception. The exception message is “A store-generated value of type 'System.DateTime' could not be converted to a value of type 'System.DateTimeOffset' required for member 'INSERT_DATE' of type 'Model.SAMPLE'.”. The inner  exception message is: “Invalid cast from 'System.DateTime' to 'System.DateTimeOffset'.”<br>
  I use ODAC 12.1012 unmanaged driver.
  How should I solve this problem?<br>Sample table script:</p>
  
  <pre><code>CREATE TABLE "TEST"."SAMPLE" 
    ( "ID" NUMBER NOT NULL ENABLE, 
      "INSERT_DATE" TIMESTAMP (6) WITH TIME ZONE DEFAULT systimestamp, 
      "TEXT_COLUMN" VARCHAR2(200 BYTE), 
      CONSTRAINT "SAMPLE_PK" PRIMARY KEY ("ID")
   USING INDEX PCTFREE 10 INITRANS 2 MAXTRANS 255 
   STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
   PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1 BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)
   TABLESPACE "SYSTEM"  ENABLE
    ) SEGMENT CREATION IMMEDIATE 
   PCTFREE 10 PCTUSED 40 INITRANS 1 MAXTRANS 255 NOCOMPRESS LOGGING
   STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
   PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1 BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)
   TABLESPACE "SYSTEM" ;
  </code></pre>
  
  <p>edmx file content:</p>
  
  <pre><code> &lt;edmx:Runtime&gt;
      &lt;!-- SSDL content --&gt;
      &lt;edmx:StorageModels&gt;
        &lt;Schema Namespace="Model.Store" Provider="Oracle.DataAccess.Client" ProviderManifestToken="11.2" Alias="Self" xmlns:store="http://schemas.microsoft.com/ado/2007/12/edm/EntityStoreSchemaGenerator" xmlns:customannotation="http://schemas.microsoft.com/ado/2013/11/edm/customannotation" xmlns="http://schemas.microsoft.com/ado/2009/11/edm/ssdl"&gt;
          &lt;EntityType Name="SAMPLE"&gt;
            &lt;Key&gt;
              &lt;PropertyRef Name="ID" /&gt;
            &lt;/Key&gt;
            &lt;Property Name="ID" Type="number" Precision="38" Scale="0" Nullable="false" StoreGeneratedPattern="Identity" /&gt;
            &lt;Property Name="INSERT_DATE" Type="timestamp with time zone" Precision="6" StoreGeneratedPattern="Identity" /&gt;
            &lt;Property Name="TEXT_COLUMN" Type="varchar2" MaxLength="200" /&gt;
          &lt;/EntityType&gt;
          &lt;EntityContainer Name="ModelStoreContainer"&gt;
            &lt;EntitySet Name="SAMPLE" EntityType="Self.SAMPLE" Schema="TEST" store:Type="Tables" /&gt;
          &lt;/EntityContainer&gt;
        &lt;/Schema&gt;
      &lt;/edmx:StorageModels&gt;
      &lt;!-- CSDL content --&gt;
      &lt;edmx:ConceptualModels&gt;
        &lt;Schema Namespace="Model" Alias="Self" annotation:UseStrongSpatialTypes="false" xmlns:annotation="http://schemas.microsoft.com/ado/2009/02/edm/annotation" xmlns:customannotation="http://schemas.microsoft.com/ado/2013/11/edm/customannotation" xmlns="http://schemas.microsoft.com/ado/2009/11/edm"&gt;
          &lt;EntityContainer Name="vm2" annotation:LazyLoadingEnabled="true"&gt;
            &lt;EntitySet Name="SAMPLE" EntityType="Model.SAMPLE" /&gt;
          &lt;/EntityContainer&gt;
          &lt;EntityType Name="SAMPLE"&gt;
            &lt;Key&gt;
              &lt;PropertyRef Name="ID" /&gt;
            &lt;/Key&gt;
            &lt;Property Name="ID" Type="Decimal" Nullable="false" Precision="38" Scale="0" annotation:StoreGeneratedPattern="Identity" /&gt;
            &lt;Property Name="INSERT_DATE" Type="DateTimeOffset" Precision="9" annotation:StoreGeneratedPattern="Identity" /&gt;
            &lt;Property Name="TEXT_COLUMN" Type="String" MaxLength="200" FixedLength="false" Unicode="false" /&gt;
          &lt;/EntityType&gt;
        &lt;/Schema&gt;
      &lt;/edmx:ConceptualModels&gt;
      &lt;!-- C-S mapping content --&gt;
      &lt;edmx:Mappings&gt;
        &lt;Mapping Space="C-S" xmlns="http://schemas.microsoft.com/ado/2009/11/mapping/cs"&gt;
          &lt;EntityContainerMapping StorageEntityContainer="ModelStoreContainer" CdmEntityContainer="vm2"&gt;
            &lt;EntitySetMapping Name="SAMPLE"&gt;
              &lt;EntityTypeMapping TypeName="Model.SAMPLE"&gt;
                &lt;MappingFragment StoreEntitySet="SAMPLE"&gt;
                  &lt;ScalarProperty Name="TEXT_COLUMN" ColumnName="TEXT_COLUMN" /&gt;
                  &lt;ScalarProperty Name="INSERT_DATE" ColumnName="INSERT_DATE" /&gt;
                  &lt;ScalarProperty Name="ID" ColumnName="ID" /&gt;
                &lt;/MappingFragment&gt;
              &lt;/EntityTypeMapping&gt;
            &lt;/EntitySetMapping&gt;
          &lt;/EntityContainerMapping&gt;
        &lt;/Mapping&gt;
      &lt;/edmx:Mappings&gt;
    &lt;/edmx:Runtime&gt;
  </code></pre>
  
  <p>Thanks in advance!</p>