allow apps to register form for the settings and admin pages

apps/user_ldap/appinfo/app.php

apps/user_ldap/settings.php

lib/app.php

settings/admin.php

settings/apps.php

settings/help.php

settings/js/apps.js

settings/js/personal.js

settings/js/users.js

settings/languageCodes.php

settings/personal.php

settings/settings.php

settings/templates/admin.php

settings/templates/apps.php

settings/templates/help.php

settings/templates/personal.php

settings/templates/settings.php

settings/templates/users.php

settings/users.php