purge stale jsbackend dependency

Change-Id: I49464147b872ff1138d48c22d9029881f6abacbf
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
make QtFeedback claim 'feedback' plugin type

Change-Id: Ie2e58724e191dd9f4790308d655266c9e637287b
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>