Allow Crowbar UI to show exceptions to users [2/2]

This change, requested by @VictorLowther, adds a dynamic (haml) error page
to the UI so that exception information is displayed to the user.

Right now, we SHOW IT ALL but the toggle code is in place so that we can
easily hide most of it later.

The reason for this change is that we return useful errors that can help
users correct their mistake and try again.  In the static error page
model, that information was being lost.

This pull also includes some doc fixes.

NOTE: I am aware that BDD is broken.  That's my next task.


 noop/roles/network-server/role-template.json |    9 +++++++++
 1 file changed, 9 insertions(+)

Crowbar-Pull-ID: c19b8a7b4da3d1881650cb5ec339457403f2d834

Crowbar-Release: development