[3939] keactrl now uses PID files to control servers

[3939] keactrl now uses PID files to control servers

src/bin/keactrl/keactrl.in
    - get_pid_from_file() - new function which returns a server's PID from its
    pid file, or 0

    - check_running() - modified to use get_pid_from_file(), sets $_pid and $_pid_file
    globals

    - send_signal() - modified to use get_pid_from_file()

    - start_server() - modified log emitted if server is already running to
    contain the PID and pid file

    - stop_server() - new function to stop a given server, IF it is running.
    reload_server() - new function to reload a given server, IF it is running.

    - get_pids() - deleted

    - Replaced use of send_signal with stop_server or reload_server to provide
    better visual feedback to users.
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