created a sqlite handler for nagios
Added a main SQL Nagios Check class and inheriting from it for SQLite and MySQL
modified path for nagios sql import
removed useless __init__ in nagios mysql check
Indentation fixes nagios_check_sql
WFU-4295 aware of the future
WFU-4295 reuse of for_timedelta_ago method
WFU-4295 change the method name