Handle sqlite get_unique_constraints() call for temporary tables

The sqlite get_unique_constraints() implementation did not do a union
against the sqlite_temp_master table like other code does. This could
result in an exception being raised if get_unique_constraints() was
called against a temporary table.
- move this to the correct location
- Added :meth:`.Inspector.get_temp_table_names` and
:meth:`.Inspector.get_temp_view_names`; currently, only the
SQLite dialect supports these methods.    The return of temporary
table and view names has been **removed** from SQLite's version
of :meth:`.Inspector.get_table_names` and
:meth:`.Inspector.get_view_names`; other database backends cannot
support this information (such as MySQL), and the scope of operation
is different in that the tables can be local to a session and
typically aren't supported in remote schemas.
fixes #3204
Merge branch 'sqlite-temp-table-reflection' of https://bitbucket.org/jerdfelt/sqlalchemy/branch/sqlite-temp-table-reflection into pr31
- changelog for #3203; fixes #3203