Install default configuration file [liftof]

[achim1]

Create and install a default configuration file during the make step. This should e.g. then be used by liftof-tui.

This will allow to make the database location a commandline parameter for liftof-tui with a reasonable default, by just giving the default config file, which should have set the proper database location.

[achim1]

This would also offer to install the database in the same location. However, we currently set the path to the DB through environment variables. However, they won't be set for the liftof binaries, since no env shell will be loaded. Make this consistent!