Rename LoginCreds to Identity, fix ViAc.user bug
Rename LoginCreds to Identity, fix ViAc.user bug

ViAc.user tries to lookup a user using an identity id. Change it to
ViAc.identity.

debiki/debiki-server-old,debiki/debiki-server-old,debiki/debiki-server-old,debiki/debiki-server-old