Cleanup + AOOSCore::register + commit Form module

Cleanup + AOOSCore::register + commit Form module

AOOSCore::register() and AOOSModule::files():
 - Added these to functions to change the way class definitions are found. Before an array of classname => file was
   stored locally in index.php, which meant that you had to add a new entry every time you added non-"module main file"
   or non-"root directory file". Now all you have to do to add a file is to call AOOSCore::register(class, path). If you
   are adding a file used by a module you should add that file to the array returned from module::files(). See
   documentation on AOOSModule::files for more info.

Cleanup:
 - Documentation
 - Cleanup the module model in AOOSCore
 - Module settings and strings are now loaded before instantiating a module and getSetting and getTranslatedString
   doesn't check if a module is loaded. This means that you can use getSetting() and tr() in all module functions.
 - Added an _is_empty method to AOOSModelRow. Adds proper checking of values before inserting to a database
 - False can also be inserted into databases now.
 - Added logging of queries to MysqlInterface. For now it logs everything - not good.
 - Fields that are primary keys have auto_increment set per default in mysql implementation

Commit of Form module. Provides functions to create different types of string from a model. Still very much WIP.