remove vpn support

here are my 2 cents

.. OpenELEC is a media center distro, not a general purpose distro. we should not support any advanced networking stuff for 0.5% of our users who want to use it. 

.. connman does not support bridged vpns. so our ovpn gui is a half-solution, anyway. I doubt it will be supported soon. and if it will be, it still does not belong to OpenELEC 

.. recently there was a busybox change that broke pptp. we all missed it and now we have broken pptp in 3.2 for long. 

.. the main focus should be on a painless distro that is able to play music/videos/livetv/whatever. for vpns there are ~ 10eur routers on market that do it well.

.. get back to the roots and focus on what is really important.

once this is approved and merged. I will move openvpn/ppp/pptp to unofficial addon repository, where in fact they belongs. I have addons built and tested already.

@chewitt @sraue please review this carefuly. think twice and I hope you'd make a wise decision.