create location specific cache tables (5.x)

Now that 5.x supports pluggable cache tables, it makes sense for location module to have it's own cache tables.

This became very apparent on my 4.7 site. I am using location module in conjunction with gmaps and my cache table exploded without clearing after a week, 85% of the entire 800mb of cache was related to location searches -- made creating nodes a nightmare locking the table!

Separating out this makes a lot of sense and is quite easy to do with 5.x. Once this module is updated to 5.x, we should create a new cache table as well to keep it separate from the general cache.