Draft: sessions: remove anonymous session
proof of concept
See discussion in !422 (closed)
Removing special handling of anonymous/defaults sessions. Fresh config
will only create default empty session. Any other session can be created
from another by saving the session with the new name. Kate will start
only to named session (either default or other) even when launched with
file arguments kate main.cpp
Pros:
- no special session handling for anon
- no need to guess where the defaults config should be taken from
- no guessing how to save defaults for sessions
- no anon session storage slot collisions
Cons:
- user might expect "new session" action somewhere