First somewhat working extraction of a Dimension class

* there aren't specs for all behaviors in place yet
* big task of wiring it up still left out
More advanced extent specs
real start_as_center support
Forgot some small specs
Move to ? methods return a real boolean
RenamedDelegate - delegate methods but rename them

* to get the magic of left calling x_dimension.start going
* will probably go and put it into its own gem... might be
  be useful for someone somewhere
Wiring up Dimensions with Dimension

* ParentDimensions specs failing due to broken direct instance
  variable get behavior to check if a value has been modified
* small bug fixes of the dimension class on the way - specs
  are GREAT
All Dimensions specs pass!!! =D ParentDimension now works.
DSL level specs fixed by using FakeElement
Add parent_dsl to the swt_app context to fix swt image fails
Parsing input values straight in the writer
Getting rid off the *_modified? methods as not needed anymore
Delegate full logic to underlying Dimension class

* before it was relying on getting the values from there, less
  less logic and I implemented the query methods either way
Fixups and further specs here and there
Use ONE_PIXEL for better clarity
Slightly nicer code formatting for element_extent= + specs
use Forwardable in RenamedDelegate instead of manual definition
Replace all occurences in RenamedDelegate
Merge pull request #675 from shoes/extract-dimension-from-dimensions

Extract dimension from dimensions