pidgin/pidgin

Add PurpleCredentialProvider as the first piece to replace the existing keyring api.

Testing Done:
Added some new unit tests and made sure they passs.

Reviewed at https://reviews.imfreedom.org/r/144/
i18n = import('i18n')
i18n.gettext('pidgin',
args : '--from-code=utf-8',
install : get_option('nls'),
)