Add plugin for german tv station ARD's live stream

Since the FIFA World Cup is transmitted one day by ZDF and the other day by ARD and support for ZDF is available, I'd like to propose this plugin. If you don't consider this plugin, please keep the pull request open for some time, so others might find it to view some football, thanks.

This only adds HDS support. There are other protocols available, too.

Since d3bd135bdc4f2d16ae9f3bbbc83979b81f77c130 is important for this plugin, I've branched from `develop`.