Implements user settings

Adds user configuration.

- non-obtrusive:
	- uses the default settings in Vagrantfile
	- only overrides if vagrant.yml is found
	- this way simply running `vagrant up` still works
- exposes all settings as chef attributes so they can be consistently used in the cookbooks (e.g. `node['foc']['app']['name']`)
- can be tested/used by changing `ip_address` 

I have deliberately kept the .default template small to get this PR passed but things could easily be expanded so we can work towards something like:

	app:
      name: api.domain.local
	  app_template: cake3

	vm:
      hostname: foc01
      ip_address: 10.36.2.10
      share_app_folder: true

Tested successfully with full rebuild.
This directory structure is this way because we prescribe the use of the app-template repository, or at least keeping your repo top-level.