Modify Config & Specs to Support Multiple Users

Servers can have more than one user on the box, SUPPORT should too.

* Add four potential user roles that SUPPORT will support during initial config
* Tweak existing model to accept a param for which user role to use
* Tweak specs to use correct values in the tests for the roles

Still to do:

* Determine how to refactor Server.new(:user_role=>['app']) into just plain ol'
Server.new; $_.users.#{user_role} rather than a new instance for each user role.
Add setup:test, Refactor Server
Default to install user role, Specs run as app
Support Multiple Users & Roles

Create SUPPORT::Server.users
Create SUPPORT::Server.user(role='install')
Add supporting specs
Refactor tests related to user behavior.
Refactor to make tests pass

6 out of 7 failing specs now green.
Refactor rake tasks to use new user setup
Refactor pubkey SCP to support multiple users

* Add support for multiple users with pubkey scp
* Ensure authorized_keys file is backed up & restored (when run via test).
* Copy user's pubkey and ensure removed in test suite.
Merge branch 'users_setup'