Various improvements to the crop tool

CCBUG: 327536
CCMAIL: wlingflute@gmail.com
Patch by  Michael Martini. Thanks!

BUG:327319
BUG:327318
CCBUG:326952
CCBUG:326933
BUG:318885

In addition a new decoration type has been added called crosshair. In
summary two new checkboxes have been added. One that allows the user to
either limit the crop to the current image size or grow the crop selection
beyond the image boundaries. The second checkbox enables center growing /
symmetric resizing of the crop bounds.