Add RPLACA/D as functions.
Add GET-PROPERTIES, GETF and (SETF GETF).

The SETF expander for GETF is weird though.
NAME is a string designator.
Simple DEFPACKAGE.

Also handles multiple :USE definitions in DEFPACKAGE.
Merge pull request #147 from Ferada/defpackage

DEFPACKAGE including USE and some more functions.