Dima Zhgenti / mbed-HDK - History

Migrate Handbook page to Readme.md

Removed section on 'where to find the HDK' as that's
the repository that the Readme is describing.

Initial import of mbed HDK

This is based on the hg repository that was hosted on
developer.mbed.org - it includes some of the same projects but also
adds the mbed 6LoWPAN Boarder Router Hat.