Remove unused common methods, correct top/left handling, removed @fixed assignment...

Hello everyone, 

this pull request entails kind of a lot since one thing always lead to another in order to keep everything working so right here we've got:

* removed right/left/in_bounds? from CommonMethods, they now belong to the dimensions object
* somewhere along the lines I removed the @fixed assignment from TextBlock and for some reason it appears to be working (at least for my eye on the manual) - #345 #371 - this however breaks the `3.times para 'hello'` sample, as those are now each one a separate line. However this is a more general problem of placing of textblock elements which I haven't yet figured out (#373)
* Slot top and left attributes now work as they are supposed to (also for non slot elements) e.g. relative to their parent, that behavior however sometimes defers from the shoes3 behavior if just either top or left is specified as I found the shoes3 behavior to be inconsistent and merely an implementation detail #217
* to support the above, every element now has an `absolute_left` and `absolute_right` which are the absolute coordinates in the app as opposed to top/left which are relative to the parent element (for elements that are always absolutely positioned like rect/oval these are always the same)
* Slot now finally also has a dimensions object
* TextBlock now also finally has a dimensions object =D

So um yeah please take a look at it and provide feedback =) 
Hope to figure out #373 soon.

Cheers,
Tobi