'absolout' stylesheet paths, added User->style

Can now use '/sth.css' in at $data['styles'] for no getTemplatePath
User->style is an array with headcolor, backcolor and textforn
Fixed bugs at models\Question
Added profile and loadquestions

LoadQ could be way faster by running only one query (SELECT * from all)
instead of 11 (select id from questions, then select * for each one)
- useless constructors, Model::_db is also static

Constructors of base class are called or class without an constructor
Added api::load, Controller->byAJAX
Added username regex in core\router

Matches all possible usernames e.g. \w{5,20}
This regex will be used when defining routes at index.php