imsettings: Move from meta-ruby to meta-xfce

It depends on xfconf which is XFCE component, no one
depends on imsettings in meta-ruby so move it close
to its dependencies.

Ideally, xfconf should be turned into PACKAGECONFIG
and this recipe then moved to meta-oe since all kind
of DE's can use it then.

For now it frees meta-ruby from unnecessary dependency on xfce layer

Change-Id: I6b5896b0db504fad49a9da5967d3493e27c627b0
Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>