Included isPriority for Task
Added isPriority to TaskAdvanced
Modified getHashtags to retrieve all hashtags.
Fixed Empty Search Bug

Now shows error if searching for empty string.
Highlight Class
Fixed Some Outdated Testcases
Better Autoswitch Functionality, Highlighting

Now autoswitches more intelligently (for add and remove).

Also completed preliminary highlight feature. Test cases to be added
after this.