Updated icon logic, shortened label, emulate native Reply

This replaces my prior Pull Request.

- Reflect change to Twitter action icon logic since 1.11
- Shortened  "RT" label plays nicer with "More..." (and any 3rd party action icons)
- Make Classic RT in-line or modal (depending on context)
- Maintain "in-reply-to"/conversation chain when Classic-RTing
- Prevent URL expansion from disturbing timeline presentation