Moved the theme libraries folder to themes/ instead of having the libraries in a specific theme's folder. This allows all themes to use all libraries and not have multiple copies of the same library
Added Image management options as constants to be used everywhere rather than passing strings

Formatted the class and comments
Updated comments for Classes!
Renamed the Sessions class to SessionsManager
Updated the comments!

Added a constant for the database table name
Updated Role class comments

Used constants for Role class DB table names
Classes
- Added comments and updated classes minimally

ScreenMessage Class
- Updated the Message type options to constants
Updated Session class comments

Deleted System class since it wasn't being used anyway!
Updated class' comments
Added an exception for invalid templates
Added a few more utility configurations to the System Config class
Updated bootstrap to register an autoload function for exceptions