frontend: small changes & cleanup in console invocation

This patch contains some changes in consoles:
1. It brings to life spice-html5 radio button.
2. It adds a newline character to generated RDP descriptor.
3. Biggest change: modification of 'Console Options' dialog availability
   condition - now user can open this dialog for VM if it's running.
4. Getting rid of common code in NoVncImpl and SpiceHtml5Impl
5. Waiting until novnc (or spice-html5) window is loaded, then
   postMessage
6. Internet Explorer version detection for novnc and spice-html5

Change-Id: I7d8b2d781f2bec3102e3efd0e1a6027372e2af46
Signed-off-by: Frantisek Kobzik <fkobzik@redhat.com>