EtherBone goes BETA

As shown at the WhiteRabbit Workshop, we now have running Hard- and Software
implementations. The EtherBone HDL core provides a slave module to go with
the WR PTP core, while the API is flexible in its role and platform independent.

Work in progress is systematic and randomized tests of both the API and the HDL core
and finalization of documentation and code cleanup.

Project status will change to Beta in the coming days.