userportal,webadmin: bring back change CD menu to SPICE console

This has been lost while moving from 3.0 to 3.1.

This patch contains:
- setting the correct menu to the ActiveX plugin (XPI
plugin does not have this functionality)
- listening to the onmenuitemselected event and firing the correct
event in response
- fix the menu item creation - new StringBuilder(int) just creates the
empty string (int param means the capacity, not the actual content)
- fix the format of the menu
- removed items which are not handled by us anymore, but handled
by the spice client itself

Change-Id: Ifdfa982da00ae333271f60795b0c17fe602e14ef
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=957611
Signed-off-by: Tomas Jelinek <tjelinek@redhat.com>