CB-6846 Fixes `Platform Add` fail on Windows slave

github: close #7
CB-6889 Change "-i" sed's argument behaviour

This now works on both mac and windows.
CB-6909 Removes platform-dependent commands

Namely shellCmd and shellRunParam from master.cfg
CB-6899 Replaces "ln -s" command

It's not working on windows slaves, so it's replaced with inline node script.

github: close #12
CB-7026 Adds info about creating necessary design documents to CouchDB