input ring history

- better error recovery
- synchronize buffer local variable
- synchronize text property (only at text insertion time)
- comint integration
- follow user

- improve error recovery mechanism
- improve support for xscheme.el
- revised remote command protocol, add spawn-site-id

- change generic function interface crdt-process-message
- added crdt--readable-encode and crdt--readable-decode
- initial work for remote command

- add error recovery to protocol
- server side error handling (by sending the client an error message)
- fix a stupid typo for the crdt--buffer-sync-callback to relocate cursor

Disable crdt-mode entirely in the cloned buffer for now.

v0.1.2

See merge request qhong/crdt.el!2