core: Add GRL_CORE_ERROR_AUTHENTICATION_TOKEN
core: Add GRL_CORE_ERROR_AUTHENTICATION_TOKEN

Add an error type for problems with authentication tokens
that require user attention, such as a VK oauth token that
requires re-login.

https://bugzilla.gnome.org/show_bug.cgi?id=744238

GNOME/grilo,grilofw/grilo,jasuarez/grilo,jasuarez/grilo,GNOME/grilo,jasuarez/grilo,grilofw/grilo,grilofw/grilo