message: updated docs for new database config
diff: @@ -14,8 +14,14 @@ at ``example/config.sample``
  "torii_port": 50051,
  "internal_port": 10001,
  "pg_opt": "host=localhost port=5432 user=postgres password=mysecretpassword dbname=iroha",
  - "working database": "iroha_working",
  - "maintenance database": "iroha",
  + "database": {
  + "host": "localhost",
  + "port": 5432,
  + "user": "postgres",
  + "password": "mysecretpassword",
  + "working database": "iroha_data",
  + "maintenance database": "postgres"
  + }
  "max_proposal_size": 10,
  "proposal_delay": 5000,
  "vote_delay": 5000,
  @@ -36,19 +42,30 @@ Deployment-specific parameters
  transactions are sent here.
  - ``internal_port`` sets the port for internal communications: ordering
  service, consensus and block loader.
  -- ``pg_opt`` is used for setting credentials of PostgreSQL: hostname, port,
  - username, password and database name.
  +- ``database`` (optional) is used to set the database configuration (see below)
  +- ``pg_opt`` (optional) is a deprecated way of setting credentials of PostgreSQL:
  + hostname, port, username, password and database name.
  All data except the database name are mandatory.
  If database name is not provided, a default one gets used.
  -- ``working database`` is the name of working database - the one that will be used to store the world state view and optionally blocks.
  - .. warning:: Deprecated behaviour: is overrided by ``dbname`` parameter in ``pg_opt`` value.
  - .. warning:: Deprecated: optional.
  -- ``maintenance database`` is the name of databse that will not be used to store any data, but only to maintain the working database.
  - .. warning:: Deprecated: optional.
  - ``log`` is an optional parameter controlling log output verbosity and format
  (see below).
  -.. warning:: Unspecified database name support is deprecated and will be removed!
  +.. warning::
  + Configuration field ``pg_opt`` is deprecated, please use ``database`` section!
  +
  + The ``database`` section overrides ``pg_opt`` when both are provided in configuration.
  +
  + Both ``pg_opt`` and ``database`` fields are optional, but at least one must be specified.
  +
  +The ``database`` section fields:
  +
  +- ``host`` the host to use for PostgreSQL connection
  +- ``port`` the port to use for PostgreSQL connection
  +- ``user`` the user to use for PostgreSQL connection
  +- ``password`` the password to use for PostgreSQL connection
  +- ``working database`` is the name of database that will be used to store the world state view and optionally blocks.
  +- ``maintenance database`` is the name of databse that will be used to maintain the working database.
  + For example, when iroha needs to create or drop its working database, it must use another database to connect to PostgreSQL.
  Environment-specific parameters
  -------------------------------
  