This adds a button and status indicator to the license-management page.
They should allow users to quickly add, editor or remove merge request
approval rules specific to license compliance.

* Adds new vuex-module that builds on existing state, actions and
  mutations for approval settings
* Adds a new vue component that contains the 'license approvals' button,
  the status text and a modal
* Adds to the rails controller to pass data via HAML to the
  store-settings
* Includes the newly added store and component within the
  policies-management app

This is implemented behind the `license_approvals` feature flag.