Jarv/newrelic log checks

This adds an optional plugin for newrelic to grep for strings in any file on disk and report the occurrences of the match to newrelic.

The extra tasks are only run if `NEWRELIC_LOGWATCH` is defined which is set to a list of templates for watching agents that are checked into the newrelic role template directory.


There are default values for both COMMON_ENVIRONMENT and COMMON_DEPLOYMENT in the `common` role, why not just use those?