MAX-94, Added configuration parameter, max_slave_replication_lag=<longest allowed replication lag in seconds> to router section.

Parameter can be changed runtime but it requires reloading of config.
Merge branch 'develop' of https://github.com/skysql/MaxScale into develop
Modified refreshInstance to support max_slave_replication_lag.
Merge pull request #8 from skysql/MAX-94

Max 94