Merge pull request #138 from liafailboy/working

Added the implementation for the button at the RootWindowContoller. Need...
Added JavaFX fxbuild file
Refactor DetermineDisplayMode method in Controller
Refactor ICommand to remove InvalidTaskNumberException
Bugfix in undo/redo logic
Add Constants.java in util package
Fix bug with next and back in UI, redirect user to the right page after command execution
Merging with Shotaro
Added category commands
Bugfixes to category commands
Merge pull request #146 from andhieka/working

Category Commands
Fix bug in UI for delete command execution
Merge with michael
Merging with Andhieka
Merge pull request #145 from mikelimantara/master

Fix bug with next and back in UI, redirect user to the right page after command execution
Removed the viewing modes from category hashmap
Set window key press handler
Bugfix: only focus at console when event text is not empty
Animations in TaskOverview
Highlight task