[IMP] ssh password option and prompt + notification option

[FI3EI2]

This commit includes two different thing, I cannot distinguish them for now so I've just committed it.

First, you can use this plugin with plain ssh password, or with a password prompt. You can use something like password = "pass123" in your deployment.lua. If there is no password set, a password prompt welcomes you and wants you to enter it. Then, it's done.

Second, I made a notification option and made it as table, because maybe it can be improved more afterwards. If you use notification = { use_cwd = true } in your plugin config, notification descriptions which show the file path will be trimmed according to current working directory, so it occupies a small space on your screen.