Support unneeded schema names in overviews queries

Fixes #420
Keep table schema of overviews base tables and use it
to support queries that use the schema name when not
strictly needed.

test/integration/mapconfig_overviews_adapter.js

@@ -75,6 +75,7 @@ describe('MapConfigOverviewsAdapter', function() {
             var expected_data = {
               overviews: {
                 test_table_overviews: {
+                  schema: 'public',
                   1: { table: '_vovw_1_test_table_overviews' },
                   2: { table: '_vovw_2_test_table_overviews' }
                 }

test/integration/overviews-metadata-api.js

@@ -40,6 +40,7 @@ describe('OverviewsMetadataApi', function() {
 
             assert.deepEqual(result, {
                 'test_table_overviews': {
+                  schema: 'public',
                   1: { table: '_vovw_1_test_table_overviews' },
                   2: { table: '_vovw_2_test_table_overviews' }
                 }