Add method .set_memory in vec::bytes for &[u8]

Add new trait vec::bytes::MutableByteVector which currently defines one
method .set_memory().
Add methods .move_from() and .copy_from() to vec

Add method .move_from() to MutableVector, which consumes another vector
and moves elements into the receiver.

Add new trait MutableCloneableVector with one method .copy_from(), which
clones elements from another vector into the receiver.
auto merge of #7210 : kballard/rust/vec-stuff, r=thestinger