Make ⌥← and ← smarter (show parent folder/hidden files and deal with combined objs). Fixes #1286

See #1287 for the discussion. This is just a new pull rebased against master

Atm hitting ← will only work for combined file objects. If you have combined say... contact objects then ← will do nothing, but that's up to the handler for 'contact' types to deal with (in 'parentOfObect:`<sup>1</sup> so it's not too difficult

<sup>1</sup> `parentOfObject`: may be worth adding it to the plugin dev ref under the 'code' section. And thinking about it, this should be made more clear - the methods here are for the class defined as the 'object handler' in the info.plist