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.
This makes it a lot easier to setup all the testing stuff. Mostly,
I'm tired of fighting Android Studio's fragility, so I want to remove
as much non-standardness as possible in the hopes of improving that
situation.
closes#534https://gitlab.com/fdroid/fdroidclient/issues/534
