tmf: Split off TmfFilterMatchesNode in two

tmf: Split off TmfFilterMatchesNode in two

Add new TmfFilterMatchesFieldNode and TmfFilterMatchesAspectNode, which
both extend TmfFilterMatchesNode (which is now abstract). This will allow
using filtering on aspects.

The aspect node is not integrated yet in the Filter View, but it could be
eventually.

Change-Id: I7206c0508eed4fbb16cc22fef97900ca31220328
Signed-off-by: Alexandre Montplaisir <alexmonthy@voxpopuli.im>
Reviewed-on: https://git.eclipse.org/r/37123
Tested-by: Hudson CI