Introduce resource namespaces

[agronholm]

It would be cool to be able to access all resources by their resource name like ctx.serializers.json. The names would also be accessible using dict-like access (ctx.serializers['json']). The biggest challenge here is making this work properly with a chain of contexts.

Perhaps even multiple levels of namespaces could be used? Like ctx.irc.networks['Freenode'].channels['#asphalt']?

This would have to be changed in all subprojects at once for consistency.

[agronholm]

This is too complicated. Deferring to a future release.

[agronholm]

I'm dropping the idea of global names for resources. They will remain namespaced under specific interfaces.