Bug 1843357: Remove deprecated jquery selectors

These are:
:first -> .first() or css first-child
:last -> .last() or css last-child
:eq -> .eq() or css nth-of-type(n)
:even -> css nth-child(odd) (odd because we're
  going from 0->1 based indexing)
And these which were not found in Mahara:
:odd
:gt
:lt

Change-Id: I512db61de687f9ea3d7a31b1514f4aa962bcb1b0