Add PMD and precommit for format and license header checking. (#1017)

Use package goal as project doesn't support earlier lifecycle phases.

scripts/check-format-and-headers.sh

@@ -0,0 +1,17 @@
+#!/usr/bin/env bash
+
+if [[ -z ${GITHUB_MODIFIED_FILES} ]]
+then
+  modified_files=$(git diff --cached --name-only --diff-filter=ACMR)
+else
+  modified_files=${GITHUB_MODIFIED_FILES}
+fi
+
+include_list=""
+for file in ${modified_files}
+do
+  include_list="${include_list},${file}"
+done
+include_list=${include_list:1}
+
+mvn spotless:apply validate -DlicenseUpdateHeaders=true -Dspotless-include-list="${include_list}" > /dev/null || true