Make parallel installable with Tracker 2.x
This MR takes the "full split" approach to making Tracker 3.x available side to side with older users of Tracker 2.x. In this MR:
- Versioned names are used for a few things:
- $datadir stuff is installed in share/tracker-3
- Developer documentation
- gettext domains
- The CLI tool is installed as tracker3
- DBus interfaces/names all bump to
org.freedesktop.Tracker3
The end result: Tracker master can get installed alongside an older Tracker version, and without disrupting its users