Task IDs start from 0, not 1

https://github.com/cs2103aug2014-f11-3j/main/issues/86

Why is this change necessary?
- Task manipulation is usually based on task IDs, e.g. delete(int
  taskIdToDelete). Previously, task IDs are the same as their arraylist
  indices and start from 0. Making task IDs start from 1 allows for more
  intuitive user experience.

How does it address the issue?
- The setTaskIds method now sets task IDs starting from 1.

What side effects does this change have?
- Callers of methods that manipulate tasks will have to take note that the
  task ID is now arraylist index + 1.
Merge branch 'master' of https://github.com/cs2103aug2014-f11-3j/main

Conflicts:
	GoogleCalAuthenticationToken
	log