Merge lp:~cjwatson/libfriends/recommend-friends-dispatcher into lp:libfriends

Drop friends-dispatcher to Recommends, to avoid pulling the run-time into cross-building chroots.

libfriends0 Depends: friends-dispatcher. I'm not normally a great fan of libraries declaring anything stronger than Suggests on run-time services, but I can sort of see the logic here since the dispatcher library will throw an error if it can't talk to the service. However, it causes practical problems.

The reason I care is that I'm trying to get "ubuntu-sdk-libs-dev:armhf" to be installable inside "click chroot" for the purpose of cross-building. libfriends0 is part of that set (via qtdeclarative5-friends0.2). Run-time services are unnecessary and unwanted, but they're normally harmless since we disable daemon startup inside "click chroot". However, in this case it isn't harmless, because friends-dispatcher depends on a number of gir* packages. gir* packages aren't currently multiarch-capable: the .typelib files differ across architectures but there's only one path available for their installation. This should probably be fixed, but it will take time. In the meantime, we need to be extra-careful to avoid requiring run-time services to be installed together with development packages, because that will cause an irreconcilable conflict in terms of which gir* packages should be installed.

I think a Recommends should be sufficient for all practical purposes - all the run-time packages that depend on libfriends0 already depend on friends as well anyway - and it will let us dodge this bullet.

See also: https://code.launchpad.net/~cjwatson/qml-friends/avoid-friends-dependency/+merge/213014