Continuation of #1309: Implementation of the resource manager server (issue #1294)

[kba]

This branch should be back in a state it can be worked on.

I did:

• base it on #1309
• merged #1315 into it (which I haven't yet pushed to the original #1309 branch so as not to close it in case I did something wrong here)
• merged master into it
• reverted the revert commit, restoring the changes of #1309 and #1315

I.e. we should be back where we were before the accidental merge, plus the @bertsky's commits from yesterday.

Only the newer commits show up here because they are already part of master though, but they are there and reflected in the worktree.