background style - not ready to merge

Hi all,

This is my next installment of addressing #711.

This branch works as expected and is almost ready to go in . . . except for a broken spec. (Comments in-line) Has to do with resource disposal . . . perhaps @jasonrclark can help? :)
I moved the corners methods from shoes to swt. My understanding is that the shoes name for this attribute is `curve` (or radius see #790) and the SWT name is `corners`. So we should not put any references to `corners` on the shoes side. Do I understand that correctly?