Fixed an issue in which userpoints cache was not updated properly

Debugging functions converted to use Usage.
String class not yet in use.

Loosely follows PSR-0.
Requires classes of the form Q2A_<Namespace>_<Class>, e.g. Q2A_Util_String
Maps to file qa-include/Q2A/<Namespace>/<Class>.php, e.g. qa-include/Q2A/Util/String.php

The init_queries plugin function now receives table names in original case.
Potentially breaking change if qa_db_add_table_prefix is manually wrapped with strtolower, however, I have not found any code in the wild that would break from this change.
Q2A core code also now using case-sensitive comparisons (there were several instances of tables not being normalized anyway).
Fixes #45.

[Bugfix - MED] Fixed the private messages reply button

Fixed an issue in which the avatar image falls down the qa-login-bar

Also set a readable default size and some more code formatting.

You wouldn’t believe how long it took to figure this one out.

Any users who ran the upgrade in the previous commit should delete the
fromhidden index and replace with separate indexes on the fromhidden
and tohidden fields.