PopulateAppMojo: change skip message back to info

I thought it would be nice not to see it in the common case where the
property is unset. But there is an integration test checking for the
message. And it's no more bothersome than other plugins that emit
one-line statuses -- e.g.:

  [INFO] --- maven-compiler-plugin:3.1:testCompile (default-testCompile) @ Example_PlugIn ---
  [INFO] No sources to compile
  [INFO]
  [INFO] --- maven-surefire-plugin:2.12.4:test (default-test) @ Example_PlugIn ---
  [INFO] No tests to run.

Author: ctrueden

src/main/java/org/scijava/maven/plugin/install/PopulateAppMojo.java

@@ -92,7 +92,7 @@ public class PopulateAppMojo extends AbstractInstallMojo {
 	@Override
 	public void execute() throws MojoExecutionException {
 		if (appDirectory == null) {
-			getLog().debug("Property '" + APP_DIRECTORY_PROPERTY +
+			getLog().info("Property '" + APP_DIRECTORY_PROPERTY +
 				"' unset; skipping populate-app.");
 			return;
 		}