Remove horde/SessionObjects and replace with Horde_Session use

Remove horde/SessionObjects and replace with Horde_Session use

NOTE: Did not change Kolab_Session usage because I have little/no idea
what is going on in there (injecting may be good for some things, but
things, but it does make it MUCH more difficult to try and track the code.
Granted, some of this may be simply that I am not familiar with the
Kolab code, however...)

Ticket #8023