[mythtv-theming] New MythTV notification center and theme...

[Jean-Yves Avenard]

Hi

Just a quick heads up, and hopefully the final addition to the
notification theme (looks like card animations won't be ready on time)

I added two states possible for errorstate StateType:
"warning" and "check"... It should be handled just like the state "error".

You can check the default notification-ui theme to see how it works.

Basically, just there to define a particular image when the
notification is either an error, a warning of a check one.