Fix storage-web installation via server-manager
1. added storage.config.global.js.erb as template and fill
 openstack-ip/storage-master
2. changed config.global.js.erb to make use of new flag. This is
  to ensure installation of storage-gui if web-gui is on different
  host than that of storage-master
3. Also added support of uninstallation of storage-web-gui

Change-Id: I2e9bbc26874de2423b719b25533584cbc45d2774