Refactored Authorization service

Just a little refactorization to the authorization service. More to come...
Only mentioning this because this is titled refactoring. Might be a matter of taste but I quite like [named parameters](http://brainspec.com/blog/2012/10/08/keyword-arguments-ruby-2-0/). They would allow you to get rid of those

<pre>
@global = !!options[:global]
@user = options[:user] || User.current
</pre>

default value statements and simplify it to:

<pre>
@global = global
@user = user
</pre>