liana: remove daemon feature

[edouardparis]

We expect user to use systemd service to manage a daemon or
to handle their process by themself.

The json-rpc server is exposed only for unix systems through
unix sockets, it is moved to its own module while the implementation
for windows is marked as TODO.

[pythcoiner]

we should check if #255 and #414 can be closed after merging this (but i don't believe libc was used only for forking the process...)

[edouardparis]

You are right, libc is required by rust anyway to call OS-level functions and system calls directly. I do not think the current change resolves #255 and #414

[jp1ac4]

I was able to run lianad, executing CLI commands and running the GUI.

As well as my comment in the code, I think you can also remove the StartupError::Daemonization variant now.

[edouardparis]

rebased and fixed @jp1ac4 comments

[jp1ac4]

ACK c14c55b.

[pythcoiner]

tACK c14c55b run GUI and lianad