API changes:
* New plugin hook system:unit_test for adding files to unit tests.
* $is_admin global deprecated; use elgg_set_ignore_access() instead.
+
+ Services API:
+ * Separated user and api authenticate processing
+ * New plugin hook api_key:use for keeping stats on key usage
+ * New plugin hook rest:init so plugins can configure authentication modules
+ * Moved auth.gettoken to POST for increased security
+ * Fixed REST POST bug #1114
+ * Fixed #881, #1216, #1217, #1218, #1219, #1220, #1298