OGR Provider: Better support for VRT data sources

[jng]

The current OGR provider has some issues around VRT data sources:

• Invalid VRTs do not bubble up as FDO exceptions because we're not checking CPLGetLastErrorMsg() for any logged errors during the OGRLayer -> FdoClassDefinition conversion process
  • As a general theme: There are many cases in the OGR provider where we are failing to check CPLGetLastErrorMsg() after an API call
• SQL layers that involve table aliases produces property names of the form {table_name}.{column_name}. This is illegal in FDO as dots are forbidden in property names.