fix operation reply to last treated client instead to reply to sender

[Houston4444]

Hi.

These PR fixes major problem with :server_control: capability : the server replies that the operation was made to the last client processed rather than to the sender.
This is related to this issue : https://github.com/original-male/non/issues/254

Here I only fixed the issue for main operations : new, open, save, duplicate, close, abort.
There was a weird indentation in 'abort', so I fixed it.
I also fixed the wrong reply of 'add' operation.

I could go a little further, but here it needs to take decisions.

At end of OSC_HANDLER( list) , the actual reply is wrong for sure, '/reply' or '/error' is missing.
I see 2 choices:

osc_server->send( lo_message_get_source( msg ), '/error', path, ERR_OK, "List done." );
or
osc_server->send(lo_message_get_source( msg ), '/reply', '');

I've got a preference for the second one, because it's not an error and a session can not have no name.

in OSC_HANDLER( quit ), do you agree that we should answer right before we shutdown the daemon?
Factually daemon should informs GUI that is quitting, it probably needs one more OSC message in GUI.

[diovudau]

Thank you very much.

[diovudau]

For the logbook:

• A decision for OSC_HANDLER( quit ) was postponed until it is clear if multiple GUIs are feasable in principle
• From the original issue, this will hopefully addresses when fixing the lockfiles
  • load_session_file , line 1193: if session's folder doesn't exists, it answers "/error ERR_SESSION_LOCKED session is locked by another process.".