ENH: DataFrame.to_sql with if_exists='replace' should do truncate table instead of drop table
#### Is your feature request related to a problem?
Dropping table when if_exists=‘replace’ will fail if the table has any objects, like a view, depending on it. Also, some databases like Oracle will end a transaction implicitly when a DLL statement like 'drop table' is issued. 

#### Describe the solution you'd like
Better alternative would be to issue 'truncate table' command instead.

#### API breaking implications

Should not have any changes on API

#### Describe alternatives you've considered

As above or a new flag if_exists=‘truncate’