Keep the release build as small as possible, so it is faster. This also
makes it less important to track all the dev tool projects for security
issues, since they are disabled on release builds.
To appease PMD, we now have a three rulesets in `config/pmd/*.xml`:
* `rules.xml`: The bulk of the rules, used by both main and test code.
* `rules-main.xml`: Rules specific to the andoid client code.
* `rules-test.xml`: Rules specific to test code.
The rationale is because checkstyle by default checks for "too many static
imports", which is a fair call. However in JUnit4 code, it is common to
import many `assert*` static methods.
Hans-Christoph Steiner