Merge pull request #2 from Longor1996/master

Changes to the plugin-system.
added more options to plugins
removed plugins folder
moved plugin viewer to help menu and added said help menu.
Added ability for the application window to save the last user position and state.
Merge remote-tracking branch 'upstream/master'
Merge branch 'master' of https://github.com/markbernard/Paint.JAVA into markbernard-master
merged pull request for application window persistence
updated build
Add dual mouse button for colours. Left button does left colour and right button does right colour. All tools and ColourChooser.
Merge branch 'master' of https://github.com/markbernard/Paint.JAVA into markbernard-master
fixing conflicts
merged two-colour option
updated build
bug fixes, new stuff etc.
last pull request had major flaws which broke lots of things. rolled back to here, and fixed bugs
moved plugin directory to (user.home)/paint-java/plugins/
re-fixed paintbrush slider bug
minor fixes
added hex-colour code input