Fix themes path and expand configuration file variable in man pages

Themes path was wrong and configuration file was hard coded.
Add man page to the systemd unit

So users know immediately which man pages he needs to read.
Merge pull request #194 from plfiorini/fixmanpages

Fixmanpages
Add support for display setup script

It is done the same way as KDM does it:
With autologin, it will be ran right after the display server starts.
Without autologin, it will be ran right after the greeter has connected to the daemon. This is needed, otherwise it'll just
show a black screen on an optimus laptop.
Detect if X is ready with the SIGUSR1 signal instead of retrying the connection
From Xserver man page:
"When the server starts, it checks to see if it has inherited SIGUSR1 as SIG_IGN instead of the usual SIG_DFL. In this case, the server sends a SIGUSR1 to its
parent process after it has set up the various connection schemes. Xdm uses this feature to recognize when connecting to the server is possible."