Default implementations for alignment rect methods.

CPView
- (CGRect)alignmentRectForFrame:(CGRect)frame
- (CGRect)frameForAlignmentRect:(CGRect)alignmentRect
- (CGInset)alignmentRectInsets

Tests needed ! Updated ReadMe.
Code cleanup
Symbolic Constant

Symbolic implementation of symbolic constant resolution. (standard
space in IB).
Not in use. In nib2cib, warn in the terminal if there is no hard coded
constant.
code style
Use bezel-inset attribute for alignmentRectInset

Tests needed but looks good.
For the intrinsicContentSize, min-size/max-size attributes are not
enough, we need a new intrinsic-size attribute.