Fixed a Bug in the PaintBrush class.
Fixed up the Image Invert Effect.

- Alpha is now correctly preserved.
- Commented out all the things.
- Did some (?unnecessary?) Pre-mature Optimization.
Added new Effect: RemoveChannels

This effect opens up a dialog with cechboxes. The checkboxes are for
each color channel that the Image has. Checking a channel will remove
the channel from the image (Set it to 0), once the action button is
pressed.
(added icons for new effects)
Added 'Reset'-Button to the Color-Info.
Added notes.

The notes tell where we will have to make changes for the layer-system.
I also added a big note-block at the beginning of the class, in which I
describe how the layer-system -should- work.
Added MORE Notes.
Bug Fixes, and more comments.
Fixed a small bug.
Put in a new LookAndFeel handling.
Added icon loading to all the Icons!
Added Icon.
Put in new LookAndFel handling. #2
Put in a fallback for the Icon loading.
(Fixed tiny mistake)
Added previewing to MakeGrid and RemoveChannels!
(how-it-could-look-like)

This is just how the 'ImageLayer'-class could basically be like. This is
by no means an actual implementation, just a bit of tinkering around.
Merge pull request #15 from Longor1996/master

(Big) Lot of small changes.