action.c: new UpdatePackage(Selected|All)
Action will attempt to update the selected packages to use the footprint
in the currently-loaded Library instead of from the .pcb file.
Assumes the footprint name (newlib filename) to load is contained in the
current element's "Desc" field (internally as: DESCRIPTION_NAME(element)).
The new footprint's mark is placed at the same location and in the same
orientation as the old footprint. The element's name, refdes, and value are
preserved. NO OTHER CHECKING is done (e.g. number of pins).
Reports and does not touch missing footprints.