In mailkernel, create a new method kernelIsRegistered() that says
whether or not the interface dealing with the mail settings has
been registered yet.

Then, in KMail::IdentityPage ctor do not attempt to access the
IdentityManager unless the mail settings interface has been
registered; since the IdentityManager lives in that interface.

This allows one to use the Kontact configuration dialog even if
KMail is not loaded.


MERGE: 4.7