[oe] script to remove orphaned files

[Frans Meulenbroeks]

As I don't really see progress on this, I am planning to take action
in a few days.
Since Khem expressed a preference to keep the files accessible, I'm
planning not to remove the unneeded patches, but instead move the to
the obsolete dir.
(alternate could be to move them to a dir called unused in the recipe dir).
Removal will be tested by verifying that bitbake -c patch remains
working on all dirs where unused files are removed.

Frans.