cleanup build file
Wrap property in a `Try`

Depending on how the resource actor is created it may raise an error. In
such a case it cannot be created and the exception should not simply
escalate. By wrapping it in a Try, we can properly handle error cases.
Move actor system to common bundle

The actor system may be used by a lot of bundles, so this is a common
stuff. Actually the more I am thinking about it, the more I want to
register everything but the core http api in the common activator.

The core bundle is just the core features that allow \BlueLaTeX to
manage people, sessions and papers. Nobody depends on it directly,
everybody needs the common features.

And if somebody needs this, lets just declare it a dependency when
needed. But this was of organizing stuffs looks better to me.