Add engine to the Gemfile

* Adds dependency on debt_advice_locator
* Updates dough-ruby to 3.2.0 or better
Set the engine's parent controller to EmbeddedToolsController
Add a tool mount point, route and a feature block
Add engine migrations to schema.rb
Add to bower.json.erb
Add RequireJS path to engine config
Add a minimal RSpec integration test
Bump gem version to 2.0.1