config file verification tool

[Zhanna Tsitkova]

Hello,
A new kerberos configuration file validation tool is now checked-in under src/util/confvalidator/validator.py.

First, the configuration file is parsed (confparser.py) and validated against formating errors (such as mismatching brackets)
Then the list of the allowed configuration attributes is compiled from k5-int.h ( based on KRB5_CONF_xxx macros in 1.8 ) and rules.yml ("Attributes:" section)
Finally, the kerberos configuration file is validated against this list of the allowed strings.
If the error, or something that validator does not understand, is found then the warning is issued in the tree-like form indicating the layer where the problem has occurred.

Your comments/feedback will be very much appreciated.

Thanks,
Zhanna