Added possibility to save simple variable types to oxregistry.

oxregistry is only prepared to set and get class instances. There is no posiibility to set and get simple types like e.g. arrays. A registry should be able to handle any type. 
I added 2 method setVar() and getVar() in order to save any type of variable to the registry. This makes it easy to use the registry as a global place for saving variables on request base.