Add mortgage_calculator gem. Add an initializer for mortgage calculator.
Add engine ToolMountPoint and routing.
correctly handle the different urls for stamp duty and mortgage affordability tools.
Features to test mortgage calculator engine integration.
If requirejs isn't available, don't load requirejs.config.
wrap mortage calculator tools in a feature flag
Merge pull request #719 from moneyadviceservice/mount_mortgage_calculator

Mount mortgage_calculator