Include filenames in loc file DEBUG lines

This will help debugging where multiple (possibly conflicting) ``*.loc`` files come from, e.g.

```
galaxy.tools.data DEBUG 2016-10-25 18:34:50,841 Loaded tool data table 'blastdb_p'
galaxy.tools.data DEBUG 2016-10-25 18:34:51,356 Loaded tool data table 'blastdb'
galaxy.tools.data DEBUG 2016-10-25 18:34:51,359 Loading another instance of data table 'blastdb_p', attempting to merge content.
galaxy.tools.data DEBUG 2016-10-25 18:34:51,375 Loaded tool data table 'blastdb_d'
```

Evidently I may have at least two copies of ``blastdb_p.loc``, but where are they?

lib/galaxy/tools/data/__init__.py

@@ -83,9 +83,9 @@ def load_from_config_file( self, config_filename, tool_data_path, from_shed_conf
                 table_elems.append( table_elem )
                 if table.name not in self.data_tables:
                     self.data_tables[ table.name ] = table
-                    log.debug( "Loaded tool data table '%s'", table.name )
+                    log.debug( "Loaded tool data table '%s' from file '%s'", table.name, filename )
                 else:
-                    log.debug( "Loading another instance of data table '%s', attempting to merge content.", table.name )
+                    log.debug( "Loading another instance of data table '%s' from file '%s', attempting to merge content.", table.name, filename )
                     self.data_tables[ table.name ].merge_tool_data_table( table, allow_duplicates=False )  # only merge content, do not persist to disk, do not allow duplicate rows when merging
                     # FIXME: This does not account for an entry with the same unique build ID, but a different path.
         return table_elems