Added skeleton for rootlayout and a menu bar. Changed css to incorporate this.
Playing around with different menu bar placing.
Added menu bar to overall view instead of root layout. Changed css to suit.
Changed blue theme to be royal blue instead of slate blue. (Cos slate blue looks purple)
Added green and red themes. Refactored darkTheme
Added popup functionality. (type popup to test) Edited css files to suit.
1.modified the modeltask class to add in the deadline attributes
2.modified sort method in logic. in specific, the sort by date method
3.added comparator for sorting by date

now program can sort by date
Merge remote-tracking branch 'origin/yongkai'
Merge remote-tracking branch 'origin/krystal'

Conflicts:
	src/gui/view/RootLayout.fxml