Drop role management

Roles are not created anymore, previously private functions for table
information extraction (CDB_UserTables, CDB_TableIndexes, CDB_ColumnNames,
CDB_ColumnType) will now be callable by anyone while only returning
information about tables over which the calling user has SELECT privilege.

Closes #36

scripts-available/CDB_DDLTriggers.sql

@@ -1,8 +1,3 @@
---LOAD 'schema_triggers.so';
---CREATE EXTENSION IF NOT EXISTS schema_triggers;
-
---GRANT EXECUTE ON ALL FUNCTIONS IN SCHEMA schema_triggers TO public;
-
 -- Table creation
 -- {
 CREATE OR REPLACE FUNCTION cartodb.cdb_handle_create_table ()