Maven output as file

For unknown reasons, displaying the build output as it runs creates a lot of delay in the compile-and-unit-test job. This MR improves performance by caching the output locally (on the runner), then uploading the file in whole once maven completes rather than giving incremental updates.

There's an abbreviated output included for at-a-glance review. The full logs are available as a job artifact, named 'maven-output.txt'. There's one such output for each parent POM (usually one in the main directory and one in "testing"). There's also a separate output file for the 'mvn test' execution, which is 'maven-test-output.txt'.

Some examples from the Schema Service:

• Latest master build, took 48 minutes
• Successful build, took 4.5 minutes
• Failed build, I introduced a compile error just so you could see what a failed build would look like.