Suppress error that happens on race condition when lock file is deleted

Now allows CACHE_PATH to be set elsewhere.

Fixes #137 properly this time. options passed through to getUidFromUsernameAndPassword, PhpClass minimum cache time reduced from 10 seconds to 0 since this catches the case of someone changing their password then immediately trying to log in with it!

Merged in changes from quick_fixes_200803 branch

Stores data in memory once it's been loaded from file

Added invalidation fnuction

Added caching ability to SQL read queries