modification in ini file to manage syslog + comments

* better comment for supported hmac algo in dns section
* adding configuration parameters in ini file for syslog
(not currently managed)
remove useless import
code refactoring on exception handling

Refactoring of zones_list and current_zone which was
repeated on all error page generations.
Permits a futur log message on exceptions with minimal work.
better loging

* handle syslog configuration
* log for deleted and added records
* log for tracebacks (debug)
* change default configuration to syslog