Fixes $cache key names where needed

Apparently some keys in the $cache array changed names, so nothing was displayed in the control panel for user variables.

This pull request fixes the following keys:

* key instead of info
* atime instead of access_time
* dtime instead of deletion_time
* ctime instead of creation_time
* nhits instead of num_hits

The replacement is done only where needed. i.e. if the array keys somehow go back to their old form, they'll be left untouched.
Merge pull request #79 from amenadiel/simplify

Fixes $cache key names where needed