GIN index uses to find posts by tag

-remove hive_post_tags table -extend hive_posts for a column with an arrays of tags id -tags are added next after a post, not in paralles as it was previously -fix bug with not removing tags for a post whose author removed tags during edition

tests/tests_api

-Subproject commit 1ffd591d38c5e764e8a3910af2d5548d8b28a55b
+Subproject commit b8f5214492bc4529c20aa8956e9446cf2ba30b44