Rename get_cat_context to get_cat_contextid
Add get_wildcard_contextids and get_dataset_item_contextids

Refs #63
Add missing concatenate operators

Refs #63
Ensure unique row IDs

Refs #63
Change get_*_contextids to get_*_categoryids

Refs #63
Update return values from get_dataset_item_categoryids

Refs #63
Fix table in get_wildcard_categoryids

Refs #63
Add all_wildcards_in_cat and all_dataset_items_in_cat

Refs #63
Support repeated IDs

Refs #63
Move all_wildcards_in_cat and all_dataset_items_in_cat earlier in locallib.php

Refs #63
Ensure all to-be-modified wildcards and dataset items are in the given question category

Refs #63
Fix bugs when adding to empty dataset
Prepare to release v1.2

Closes #63