Terminal compatibility: Pass vttest 2 and 3

[imsnif]

This makes Zellij pass vttest 2 and 3. Things that were required:

1. Properly handle tabstops (namely setting and clearing them)
2. Handle cursor save/restore position
3. Handle character-sets (this should address the various q instead of separating lines issues)
4. Support for disabling linewrapping
5. Various other small behavioural fixes

Terminal compatibility should definitely improve, but we still have a bit to go. If your app is still not working, please stay tuned! (and open an issue if none exist yet)