Fixes for screen capture related issues.

MAGN-553 Screen capture only work within original canvas borders
MAGN-742 Screen capture should not capture the grid

Improved screen capture to 150dpi for better image quality. This value could be modify in Configurations.cs.
Fix test cases for Capture Image.
Merge remote-tracking branch 'upstream/ChocoButterUI' into MAGN-553
Refactoring fix for screen capture.
Screen Capture retrieves Current System DPI
Merge pull request #909 from l2obin/MAGN-553

Fixes for screen capture related issues.