Added more command-line parameters.
Added command line parameters for jline.

Signed-off-by: William Lebel <lebelwilliam@gmail.com>
Handle invalid command line parameters with a warning only.

This commit changes the server startup code so that it starts even when
encountering an unknown option. This change is motivated by the fact that most
server hosts provide the nogui option in their startup script and would thus
prevent the server from starting.
Further tidied up command line handling.
Added ClientSettings to players for storing settings sent by the client.
Handle torch placement (see #119).
Toggle between normal and inverted daylight sensor on interact.
Use difficulty set in config (thanks @wow4201).
Added config option for keeping spawn chunks loaded.