Adding Select2 jQuery library

Bug 1323921: This jQuery library turns "select" tags into autocomplete fields

Change-Id: Idc68bcfbe08d5ba5dfae47b748f43072abb09a94
Mahara compatibility changes for Select2 external library

Bug 1323921

Change-Id: I77827d61f77cc9698b1799e3fb2e334670a19b72
Signed-off-by: Yuliya Bozhko <yuliya.bozhko@totaralms.com>
Merge "Adding Select2 jQuery library"
Merge "Mahara compatibility changes for Select2 external library"