add get the four corners of a screen region
add create custom screen region on a given screen id
add copy the content of a screen region
add an example on how to use copy region feature
add show canvas on the region to be copied
Merge branch 'copyRegion' of https://github.com/kalharbi/sikuli-api

Conflicts:
	src/main/java/org/sikuli/api/robot/desktop/DesktopKeyboard.java