…S features

…es FTS feature

* Add extentions pg_trgm, unaccent, btree_gin repectively for trigram fuzzy
	search, unaccenting strings and using gin index.
* Add column tokens TSVECTOR to alias table to add tokenized names.
* Add view master_entities to extract all the master entities.
* Add materialized view search_mv holding all the search relevant information
	about master entities.
* Add materialized view search_words_mv for all unique tokens (used to suggest
	the next best query).
* Index fts_search_idx on materialized view search_mv column tokens to for quick
	FTS.
* Add view untokenized_names holding all master entities with empty tokens,
	signifying unsupported names by to_tsvector.
* Index untokenized_names_idx on materialized view search_mv column names to aid
	quick view untokenized_names query.
* Unique indexes on search_mv and search_words_mv to aid REFRESH CONCURRENTLY
	command.

    * Add function token_creator to tokenized name and enter it as token field in
            alias table
    * Add function refresh_mv which refreshes all materialized views linked with
            FTS - search_mv and search_words_mv
    * Add triggers for insert/update on each entity_header to call the refresh_mv
            function each time a new entity is inserted or updated (master revision).
    * Add trigger for insert on alias to call function token_creator.