TransformedSource: a source that allows an extra, manually edited transformation

This transformation decorates the original transformation of the source.
It allows the user to manually register a source with respect to its
original transform.
Now we need to have a UI to modify this transform...
Signed-off-by: Jean-Yves Tinevez <tinevez@pasteur.fr>
added jdom dependency
replaced org.w3c.dom stuff by jdom2
Prototype of manual editing transformation.

- Select the source you want to modify.
- Go into fuse mode.
- Press 'T'.
- Move around in the viewer. The target source does not move, while all
  the other move.
- Press 'T' again; the new transform is 'stored'.

Still plenty of bugs: the manual transform is not stored it seems.
Signed-off-by: Jean-Yves Tinevez <tinevez@pasteur.fr>
Merge branch 'jdom' into transformed-source
revert formatting changes.
split TransformedSource transform into incremental and fixed part.
fix transform after leaving transform edit mode.
add TODOs for ManualTransformationEditor
ManualTransformationEditor un/registers with SpimViewer as a Listener when de/activated.
Prepared support for transforming multiple sources simultaneously.
Use the new ImgPlus in imglib2 meta package

Signed-off-by: Jean-Yves Tinevez <tinevez@pasteur.fr>
ManualTransformationEditor: <ESC> aborts, <R> resets extra transform to identity
Merge branch 'transformed-source'

Conflicts:
	pom.xml
undo formatting changes