adds document about metrics being tracked
Wrap all json strings and string values in double-quotes
CDB-3256 adds headers based on affected tables when creating a layergroup via HTTP GET
Changes travis configuration to be similar to windshaft one
Sets PGUSER environment variable
CDB-3256 fix test and adds a couple more of tests for testing the no-cache scenarios
CDB-3256 Prepares 1.12.0 Release