Add compatibility shims for deprecated features that Mozilla won’t implement

[ExE-Boss]

Add a script that maps the following into extensions that use deprecated functionality:

Deprecated funtion	What to map to
extension.onRequest	runtime.onMessage
extension.onRequestExternal	runtime.onMessageExternal
extension.sendRequest	runtime.sendMessage

Deprecated manifest key	What to map to	Notes
options_page	options_ui	Fixed by #58

Examples of extensions that use deprecated functionality:

• Lazarus: Form Recovery (On AMO)

[Noitidart]

Thanks very much for your detailed post. I will keep this in mind in the rewrite :)

[ExE-Boss]

Also, keep in mind that there is a fair bit more deprecated functionality in the Chrome extensions API that wasn’t added to the WebExtensions API. (The ones I put into the table were just the ones that came to mind)