CRM-14479 - Implement "/civicrm/a" page

CRM-14479 - Implement "/civicrm/a" page

This page is a container for Angular-based pages. To develop a new Angular-based page,
one would:

a) Create a JS file which defines an Angular module. (The file should start
out with "var myModule = angular.module(...)".)

b) Register the module-name/file-name. This can be registered either by:

 - If writing a CiviCRM extension, then implement hook_civicrm_angularModules.
 - If writing a CiviCRM component, then implement getAngularModules().