Updated Controller

Add:
- calls addTask(name, description)
Edit:
- calls editTask(taskID, name description)
Date:
- calls editDate(taskID, day, month, year) //date is in int
Completion tag:
- calls switchTag(taskID) //just flips done/not done
Workload:
- calls editWorkload(taskID, WL) //WL is in int
..... others under construction
Updated a bit more

- updated readme
- included a public function in controller
handleError(String), which does nth so far, but is called by other
classes in case of exception/error