Fixes#555
Before this change, we were resolving HLL function and type Oid without qualified name.
Now we find the schema name where HLL objects are stored and generate qualified names for
each objects.
Similar fix is also applied for cstore_table_size function call.
All citusdb references in
- extension, binary names
- file headers
- all configuration name prefixes
- error/warning messages
- some functions names
- regression tests
are changed to be citus.