Adds parameter to User\Session:getUser() to skip validation, and
modifies OC_App::getEnabledApps() to use this parameter to skip
session validation when loading apps.

Signed-off-by: Scott Shambarger <devel@shambarger.net>

)

Adds a new AppManager method which identifies when all app types
are protected, loads all apps (without checking user filters).

This has the intended benefit of avoiding calls to
User\Session:getUser() for these app types, and likely
invalidating the session before user backends are loaded.

Signed-off-by: Scott Shambarger <devel@shambarger.net>