Add support for a basic installer

This change adds support for a basic installer using a new prefix
called 'install'.

We can add check and load actions to controllers using this prefix to
add installation support.
Add basic installer framework

This change makes it easier and streamlines the model installer
creation process.

- Add a component to simplify installation checks
- Add a piece of JavaScript to check the installation status using AJAX
- Add a layout for the installer
Add role and permission installers

This adds installers to the roles and permissions controllers. The role
controller actually contains a way to load missing roles in the
database. The permissions controller does not however.