Display constraints when creating a machine.
Incorporate review feedback.
Hook up the onboarding code to work with the new state system
Merge pull request #379 from hatched/fix-1328932

Hook up the onboarding code to work with the new state system

Fix for: https://bugs.launchpad.net/juju-gui/+bug/1328932

#### To QA
1. Follow the steps in the bug, onboarding should work as expected.
2. Clear local storage, visit a url with charm details, the onboarding shouldn't show.
Merge pull request #375 from kadams54/create-machine

Create machine

This adds the ability to select the constraints before creating a new machine.

A continuation of https://github.com/juju/juju-gui/pull/366

QA:
- open the machine view
- click "Add machine"
- a constraints form should appear
- if you wish fill in some constraints
- click create
- a new machine token "new0" should appear

To test cancel with unplaced units:
- drag a service to the canvas
- open the machine view
- drag the unplaced unit to "Create new machine"
- the unplaced unit token should have been removed and a constraints form should appear
- click cancel
- the unplaced unit token should  reappear