Add python tuskar client

Add python tuskar client
Heat version to latest stable-juno

We need latest stable-juno version of heat, which has for example
fixed stack-update.
Also adding a note about variable needed to be set, so this
reporefs are actually used.
Calling Tuskar CLI properly

As tuskar CLI is added properly here
https://review.openstack.org/#/c/130714/ ,
we can call it properly in instack now.

This was also breaking the packaged install. Fixing also
path for Tuskar templates, which also breaks the packaged
install.
Store keystone certificates to Tuskar

At first cleaning the ugly sed of the json file. But also stores
these certificates to tuskar. As tuskar should hold all the
parameters. Otherwise it would not be fully compatible with UI.