Generalise finaliseCap to more than just IRQs

Changes finaliseCap to return a generic definition of cleanup information that
needs to be done, instead of just encoding an IRQ number. The post deletion information
is encoded as a `cap_t` due to the capability type already being a union of all
the possible information. Aside from providing a properly generic mechanism the motivation
is to support a similar cleanup phase for I/O ports in the future.

Fix licenses (the rest)

s/D61/DATA61/ in license headers for consistency

Move cap definitions from objecttype into header