generic share & action extensions

[kfix]

Shipping services on OSX is very clunky, I'd much rather build a generic NSExtension for each app that can accept any URL when selected via "Share" menus all over the system.

This will not be helpful for clipping text (like bare phone numbers and street addresses) but Safari already does some auto detection of those to make tel: and maps: urls so that's fine.

[kfix]

Safari supports NSExtensions as well, although not in the context of a Shareing item:
https://developer.apple.com/library/safari/documentation/Tools/Conceptual/SafariExtensionGuide/CommunicatingwithyourOSXApplication/CommunicatingwithyourOSXApplication.html#//apple_ref/doc/uid/TP40009977-CH23-SW8

[kfix]

moar links:
http://asciiwwdc.com/2014/sessions/205
https://developer.apple.com/library/mac/documentation/General/Conceptual/ExtensibilityPG/ShareSheet.html#//apple_ref/doc/uid/TP40014214-CH12-SW1
https://github.com/mozilla/firefox-ios/blob/master/Extensions/SendTo/ActionViewController.swift
https://github.com/mozilla/firefox-ios/blob/master/Extensions/ShareTo/ShareViewController.swift