Support schema overrides allowing tables with X/Y/Z columns to be configured as point feature classes

[jng]

It would be nice if we can override the SQLite logical feature schema (just like with the ODBC provider) so that tables with X/Y/Z columns can be defined as point feature classes.

The current workaround is to create a view on the table with a computed column which is the X/Y/Z column values in its WKT form. Then this view needs to be registered into the FDO metadata table for the provider to correctly interpret it as a point feature class.

Not the most pretty and performant solution.