Provide a way for custom packages to override views used by core and con...

This code will allow custom packages to override the views used by custom & contrib packages (such as the home page)

It creates a provider called $viewPathProvider.  Routes are defined as so:

    $stateProvider
      .state('home', {
        url: '/',
        templateUrl: $viewPathProvider.path('system/views/index.html')
      });

A custom package can then override the view used by doing this:

angular.module('mean.mycustompackage', [])
	.config(['$viewPathProvider', function($viewPathProvider) {
		$viewPathProvider.override('system/views/index.html', 'mycustompackage/views/homepage.html');
	}]);