Move net_demo_installer to contiv/install

[neelimamukiri]

We seem to have a requirement to run the install from a node in the host.
So allow installing ansible on one of the nodes and running installer from there rather than as a container from an external host.

[neelimamukiri]

For reference, some of the changes between net_demo_installer and the current installer:

1. Service VIP is the IP of the control interface of a master node, rather than the IP of eth0 or the first interface
2. Only nodes explicitly marked as role: master are used as master nodes as opposed to net_demo_installer where all nodes are master nodes
3. Current ansible installs etcd as stateful by default