Bug 549532 - Deleting a view should also clean the plugin.xml

Add DeleteParticipant to handle the cleanup of the plugin.xml.
Also add tests for the participant.

Change-Id: I2c4c6682fda7d54739cd782b08ce0b958d0ffde7
Signed-off-by: Eugen Neufeld <eneufeld@eclipsesource.com>
52 files changed