Crypto.ECC: Unified the APIs for Curve and Curve25519. new_scalar(), get_x() and get_y() now return coordinates in the preferred representation for the curve (ie either as a Gmp.mpz or as a string(8bit)). create(), set() and `*() accept that same value as argument. Added get_{x,y}_{num,str}() to get a specific representation. jose_name() now has a default implementation that returns UNDEFINED. Added default implementation of get_curve(). Curve25519 now has a Point subclass.