add an applet to b2d init; b2d start; export DOCKER_HOST=tcp://localhost...

...:4243

this may well simplify things for the new user - 

- run installer
- open Applications
- click Boot2Docker Start icon

leaving them with a running b2d vm, and in a terminal session with DOCKER_HOST already set.

ie - as simple as the Windows experience.

(I will add some more hints to it later - need a haircut :) )