providers/multipart: RESTEASY-754 Support apache-mime4j 0.7.2

Apache mime4j 0.7.2 has been out for a while now. Update the
multipart provider to support it.

The multipart provider had extended some classes from 0.6 that are
nolonger available in 0.7.2. Therefore a new approach was taken of
copying a few bits of code from mime4j and rewrite small parts.

See Mime4JWorkaround.java, and Mime4jWorkaroundBinaryEntityBuilder
for all such code.