host only interface / dynamic IP with fixed hostname

* creates a host only network in virtual box if not exist
* will ask to modify if a network exists which does not use the defined settings
* add a second interface to the VM with a host_only network - **needs #197 to work!**
* updates DOCKER_HOST in .bash_profile
* updates docker in /etc/hosts with the actual IP of the docker daemon on the host only network

**REQUIRES BASH** to work!

will ask for your docker vm user password if you not placed your public keys in the VM on every start to validate the current IP.

_this implements the requirements of #93 except for ***not offering a static IP*** - this allows to have multiple VMs to use the same host only network and talk to each other._