This change declares two new functions:
`master_update_table_statistics` updates the statistics of shards belong
to the given table as well as its colocated tables.
`get_colocated_shard_array` returns the ids of colocated shards of a
given shard.
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.