Revising settings to correctly save layout urls

- settings HTML updated to change `ng-show` to `ng-if` for `url-entry` directive to avoid the problem of it validating when not being displayed
- adding a `config` module in config files to define value `defaultLayout` for settings app, the value is temporary for testing purposes
- controller logic updated to remove previous $setValidity logic which is no longer needed and also added `layoutURL` to `params` and `customURL` to `additionalParams.layout`
- settings app updated to use new `config` module
- tests fixed