Allow JavaDNS to be disabled as part of resolving outstanding build and test issues

[anjackson]

This is an attempt to resolve some issues that have been de-stabilising the build process on Travis CI, and may have contributed to #175 & #176.

• Allow JavaDNS to be disabled so that the StatisticsSelfTest becomes reproducible on a wider range of networks (specifically, where DNS cannot be used to resolve localhost).
• Make OneLineSimplyLayout part of commons to avoid confusing errors (see Missing OneLineSimpleLayout class file #173).
• Use the build output folder as a temporary directory space rather than /tmp/.

Travis CI aggressively wipes /tmp/ so the build fails seemingly at random if we use it. I suspect the assumption that /tmp/ is a good place to write to is also part of the problems seen in #175 and #176.