Separate cache table for HS because it needs to be shared by all web servers

Into HS cache table is used to store info about HS_form_build_id.

If we use a shared frontend (load balancer with 2 or more webserver) we must share cache data (otherwise form validation fail). Actually is required share cache table, but this table contain also a lot of other info and is preferable use a different table to share this data (like cache_hierarchical_select).

Patch create cache_hierarchical_select table (install, uninstall and update functionality).