wpa_supplicant: add DBus method for changing debug parameters

wpa_supplicant: add DBus method for changing debug parameters

Add a new DBus method "setDebugParams" which takes the parameters
debug_level, debug_timestamp and show_keys as input and updates the
internal debug variables accordingly.

To change the debug level, enable/disable timestamps and enable/disable
show_keys the following dbus-send command can be used:

dbus-send --system --dest=fi.epitest.hostap.WPASupplicant --print-reply
/fi/epitest/hostap/WPASupplicant fi.epitest.hostap.WPASupplicant.setDebugParams
int32:0 boolean:false boolean:false

Signed-off-by: Helmut Schaa <helmut.schaa@googlemail.com>