#75: Made Task comparable.
Clean up
Used FXCollections to sort the table.
Merge commit 'a62bfe8fd5e1d2c38ed84daf6a26bb1e4b4011f3' to use the Task comparator.

Conflicts:
	src/command/CommandEnum.java
	src/common/Task.java
	src/main/controllers/TaskListViewController.java