[Addons] Rebrand extension points from xbmc.FOO to addons.FOO

First commit just replaces everything from xbmc.FOO to addon.FOO.
The second commit adds legacy support for xbmc.FOO and makes sure, that we translate the old xbmc.FOO to the new ones so we only have to deal with the new extension points (outside of CAddonMgr).
All addons that are already in the db, will still have the old extensions points, so the 3rd commit upgrades them to the new ones.

There is only one case where addons might break. When they use ```Addon::getAddonInfo("type")``` as this will return the new extension point name. Not sure how many addons use that.

The 4th commit changes all 'core' addons to use the new extension point names. I'm not sure if that makes sense right now. Is Helix (if this makes it into helix) going to use the same repo as gotham?