Various code optimizations, ensure session exist when starting new daemons

[kkga]

• wip: use types for session, client, buffer
• add KakContext struct
• use new types in commands
• use new type in connect
• add short descriptions to commands
• move filepath to kak package
• kak.Create -> kak.Start
• update preview cmd in scripts
• move tmp reader to separate file
• use filepath in run
• scripts: ensure normal mode before executing keys in kks-lines
• ensure session exists when starting new kak sessions
• close fsnotify watcher and cleanup tmp files immediately after reading
• use tmp naming in cat