This also removes the powermock dependency. Although powermock is a
fine library, it currently prevents dropping Junit4. And since we only
use the Whitebox API of powermock, this simply replaced powermock's
Whitebox with our own.
and FileTestUtil in favor of commons-io. This is required because
Eclipse won't put src/test code into the classpath of src/main
code (even though gradle was configured with an according
dependency).
The previously used approach of
project(':smack-core').sourceSets.test.runtimeClasspath
caused the 'eclipse' target to produce duplicate classpath entries in
.classpath when run with Gradle >= 2.6. It also relied on Gradle
internals.
Instead we now use
project(path: ":smack-core", configuration: "testRuntime")
project(path: ":smack-core", configuration: "archives")
to be able to use test classes from other subprojects (usually
smack-core) in e.g. smack-extensions. The 'archives' configuration
includes the test jar.
See also https://discuss.gradle.org/t/11784
Thanks to Lari Hotari for helping with this issue.
