removed redundant .sql file with DDL
updated wikia_home_page_collections_city_visualization DDL
added primary key to city_visualization table
added memcached layer
removed unused method
moved PK at the top of DDL on backend team request
we want to be able to add a wiki to several collections
Merge branch 'collections-fix' into DAR-323
Merge pull request #911 from Wikia/DAR-323

DAR-323: Clean-up