BugFix: Made timeline view update now. Yays.
When I renamed tentativeview to timelineview somehow it didn't change in TimelineViewManager
Updated the way logic feedbacks to gui. Made delete more intuitive.
Made scrolling up/down to page up/down instead of enter/backspace
Made commandline show "delete " to prompt users to delete the possible line numbers.
Updated ModelTask's string formatters to be final static, as they only need to be declared once. Changed variables to be package-private for sub-classes to inherit
Skeleton class for ModelTentativeTask. Will move methods to it later.
Changed constructor in ModelTask used for copying to a method that returns a new ModelTask. Updated Iterator used in CommandFactory and the copy function used.
Skeleton to override copyTask method in ModelTentativeTask.
Moved methods from TentativeTask to ModelTentativeTask to separate the gui and logic.
Merge remote-tracking branch 'origin/krystal'