Added configuration/customization

This commit adds and changes several things:
* Add a configuration model for Cms::Fortress
* Allow for custom roles to show up in the left nav bar if they are configured (see README)
* Make page workflow and page caching optional
* Remove the empty dashboards per category and instead forward to the first page in the category
* Remove the parent abilities, i.e. "Settings", "Design", "Contents" - instead, the top nav bar will show up if the user has any ability in the category
* Remove .rbenv-gemsets, .ruby-version and .rvmrc - these should not be in the repository
* In the Role Details page, change the title of the details to the humanized name instead of the command
* Automatically copy roles.yml to the parent application for easier customization