Added events map property

This allows for events to be mapped to plugin groups. This helps on avoiding hardcoding importPlugins calls on model action methods.
onUserAuthorisationFailure is documented as a user event.

Left authentication plugins loaded for BC.
onContentPrepareData is a content event.

Left user plugins loaded for BC.
onContentPrepareData is a content event.

Left user plugins loaded for BC.
Synced with latest JModelAdmin changes.

Load user plugins for save and delete events. Load content plugins for change state events.
Synced with latest JModelAdmin

Load user plugins for save and delete events. Load content plugins for change state events.
Synced with latest JModelAdmin changes.

Load extension plugins for save and delete events.

Added onExtensionBeforeDelete and onExtensionAfterDelete for consistency.
Do not hardcode plugins loading.
Cleanup.
Synced with latest JModelAdmin changes.

Load extension plugins for save, delete and change state events.

Added onExtensionBeforeDelete, onExtensionAfterDelete and onExtensionChangeState for consistency.
Synced with latest JModelAdmin changes.

Load extension plugins for save, delete and change state events.

Added onExtensionBeforeDelete, onExtensionAfterDelete and onExtensionChangeState for consistency.
Trigger save and delete events.
Trigger save events.
Synced with latest JModelAdmin changes.

Load extension plugins for save, delete and change state events.

Added onExtensionBeforeDelete, onExtensionAfterDelete and onExtensionChangeState for consistency.
Trigger save events on component config save.
Synced with latest JModelAdmin changes.
Merge branch 'staging' of https://github.com/joomla/joomla-cms into staging