Add new list hideIndexes and develop new function by hypo_get_relation_info_hook.
User can hide or unhide existing index and hypothetical indexes.
When user set hide existing index and execute EXPLAIN, it will scan the same oid in hideIndexes and remove it to make query-plan can't use it.
Add regression tests for hiding existing indexes.
Update to version hypopg--1.4.0.
Provide simple examples of using the hide series functions in README.md.
Update doc about hypothetically hide existing indexes.
