Add command for list rpc management in Makefile.

Add command for list rpc management in Makefile.

make start-listrpc
  -> starts the list RPC daemon in background. Logs are
    not accessible in this mode, so this cannot be used to debug
    this rpc server (but this can be used to work on the website).

make stop-listrpc
  -> stops an instance of the RPC daemon started using make start-listrpc

make restart-listrpc
  -> stops + starts

make start-listrpc-fg
  -> starts the list RPC daemon in foreground. Logs are accessible,
    the daemon can be stopped using ^C

Important Note: You can change the port of your RPC daemon by adding a
parameter rpcport in the Lists section of your platal.conf:

[Lists]
rpcport = "42420"

Signed-off-by: Florent Bruneau <florent.bruneau@polytechnique.org>