Merge with trunk

mod_admin_telnet: Use module:shared() to expose commands table and default console environment

moduleapi: Add module:shared(), a way to easily share data between multiple loaded modules

moduleapi: Add module:depends(), a way to safely depend upon another module at runtime

modulemanager: load(): Return and use the correct module object

util.helpers: After nearly 'fixing' this code, I conclude it instead only deserves a bigger smile

modulemanager: Cleanup some unused variables, imports, whitespace and add a comment.

modulemanager, moduleapi: Replace hooks multitable with an event_handlers map stored in individual modules. Also adds module:hook_object_event() to hook events on any util.events compatible object.

modulemanager: Drop unnecessary prosody_events local

modulemanager: Some reorganisation. Only external change is (should be) that module-unloaded and module-loaded are no longer fired when reloading a module, the new event module-reloaded is fired instead.