Engine: System Groups: update initial migrations for nutupane impl

When the system groups nutupane was created, a couple of modifications
were made to the schema.  Those were tracked in the 'remove' migrations
that are being deleted with this commit.

We are currently in the process of rebasing the engine branch
off of devel; therefore, to minimize migrations, this commit
rolls those changes in to the initial 'katello_tables' migration.
Engine: add less-rails to the gemspec
Engine: pathing fixes for new functionality from devel branch

This commit addresses several pathing changes that needed to be
made to support enhancements made in the devel branch after
pulling them in to the engine.
Engine: test fixes after rebase with devel branch

This commit contains fixes that are needed to ensure
'rake test:katello' runs successfully after the rebase
of engine branch with devel branch.

Note: the changes to the models to incorporate 'class_name'
were required to support the association_test which
treats model associations as the base model
(e.g. Provider) vs the namespaced model (e.g. Katello::Provider).

Results with commit were:
test: 1082 tests, 2082 assertions, 0 failures, 0 errors, 5 skips
spec: 1283 tests, 2477 assertions, 0 failures, 0 errors, 4 skips
Engine: fix font-awesome and rabl pathing after engine branch rebase

This commit contains 2 small fixes:
1. updates to address font-awesome pathing issues on old tupane pgs
   (courtesy of ehelms... thx!)
2. fix pathing in several rabl files
Engine: modification to fix conflict in namespace with core

Foreman recently introduced a modified navigation, which uses
class name (Menu) which conflicts with the katello engine.