Add support for SWT.IMAGE_GRAY and SWT.IMAGE_DISABLE flags

Original SWT code transforms source image data to produce their
disabled/grayed representation.

- add IMAGE_GRAY and IMAGE_DISABLED to SWT class
- copy original SWT transformation code to coresponding Image
constructor

317439: Support for IMAGE_GRAY and IMAGE_DISABLE
https://bugs.eclipse.org/bugs/show_bug.cgi?id=317439

Change-Id: Iecdacbdb2a1ab1ee6e11eb47a999cf51289bdab8
Signed-off-by: Ivan Furnadjiev <ivan@eclipsesource.com>