Allowed custom validsettings for other non-boolean perl variables.
Add tests for enum variables.
Moved the last of the logging-related variables to perl

We seem to have picked logpath as the string variable we test in
tester.c.  Since this is no longer in C, I've replaced it with
personalbell (no particular reason for that choice).
Added a logadmin variable for logging admin messages
Ignore kerberos instances in the sender and recipient when logging

This fixes trac-#151 (Handle logging of personal zephyrs from different
instances of Kerberos principals sanely).  Stripping the instance is
only done for the filename, not for the actual log contents.
Log different realms to different files