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/
subdir('reference')
if ENABLE_GTK
pidgin_man = configure_file(
input : 'pidgin3.1.in',
output : 'pidgin3.1',
configuration : man_conf,
install : true,
install_dir : get_option('mandir') / 'man1')
endif
if enable_consoleui
finch_man = configure_file(
input : 'finch3.1.in',
output : 'finch3.1',
configuration : man_conf,
install : true,
install_dir : get_option('mandir') / 'man1')
endif