pidgin/pidgin

Make the CredentialManager the only thing in charge of its preferences.

Testing Done:
Started pidgin3 with an empty config directory, verified the notify dialog didn't pop up. Set the preference and exited a few times to make sure everything was working properly.

Reviewed at https://reviews.imfreedom.org/r/1079/
#define PIDGIN_ICON 104
#define PIDGIN_TRAY_AVAILABLE_4BIT 105
#define PIDGIN_TRAY_AWAY_4BIT 106
#define PIDGIN_TRAY_BUSY_4BIT 107
#define PIDGIN_TRAY_XA_4BIT 108
#define PIDGIN_TRAY_OFFLINE_4BIT 109
#define PIDGIN_TRAY_CONNECTING_4BIT 110
#define PIDGIN_TRAY_PENDING_4BIT 111
#define PIDGIN_TRAY_INVISIBLE_4BIT 112