Tests: Add test for exported JARs

Add a unit test to test the new functions to export JAR targets. The
test builds three sub-projects: two that generate and export a JAR (one
does a build-directory-only export, one an install-only export), and a
third that consumes the first two as imported targets.

Tests/JavaExportImport/InstallExport/Bar.java

@@ -0,0 +1,11 @@
+class Bar
+{
+  public Bar()
+  {
+  }
+
+  public void printName()
+  {
+    System.out.println("Bar");
+  }
+}