* Metadata cache now handles a 0 string. #1227
* ElggPlugin get() now works with 0. #1286
* Metadata __isset() now works for falsy values (except NULL). #1414
+ * clear_plugin_setting() now only clears a single setting.
API changes:
* New plugin hook system:unit_test for adding files to unit tests.
* annotation_id column added to the river database table.
* remove_from_river_by_annotation() added.
* unregister_elgg_event_handler() and unregister_plugin_hook() added. #1465
+ * clear_all_plugin_settings() added.
Services API:
* Separated user and api authenticate processing