grim/pidgin

Create a new PidginCredentialsPage and associated widgets for the preferences window

Testing Done:
Compiled and ran locally with the secret service provider from https://reviews.imfreedom.org/r/401/

Reviewed at https://reviews.imfreedom.org/r/402/
syntax: glob
.*.swp
.DS_Store
.flatpak-builder
*.pyc
*~
\#*\#
subprojects/*/
syntax: regexp
^build(.+)?\/
win32-install-dir(\.release)?