tool: add changelog_gen.sh to automatically generate changelog

scripts/changelog_gen.sh

@@ -0,0 +1,15 @@
+# Generate CHANGELOG_LAST.md from changes since the last version tag. (vx.y.z-dev tags are ignored)
+# CHANGELOG_LAST.md can be edited manually if required and manually added to docs/CHANGELOG.md
+#
+# Requirements: 
+#    npm install -g auto-changelog
+#
+# Usage: 
+#    changelog-gen <next-version>
+#
+# Example: if the latest verision is v5.6.7 the followings can be used for bugfix, minor or major versions:  
+#    changelog-gen v5.6.8         
+#    changelog-gen v5.7.0         
+#    changelog-gen v6.0.0         
+
+auto-changelog -t changelog-template.hbs -l false --latest-version $1 --unreleased-only  --tag-pattern ^v[0-9]+.[0-9]+.[0-9]+$ -o CHANGELOG_LAST.md