[DAEMON-321] @appcd/plugin-titanium: ti add command

Today, you use "ti create" or "appc new" to add a watchOS app to your Titanium app. This is confusing because adding a watch app requires context. An "add" command explicitly defines that context. Besides Watch apps, iOS extensions, and maybe a storyboard launch screen, I'm not sure what other components there would be. This command will use the same template system used by "ti new".

Usage

ti add

ti add --type <type>

Is this ticket even needed?

There's discussion stemming from TIMOB-26807 about there being a persistent Xcode project instead of Titanium build generating one. If we have a persistent Xcode project, then this ticket is probably invalid since users can just open the Xcode project and add the target directly.