Port to Gradle based build

[johnthagen]

Follow: https://plugins.jetbrains.com/docs/intellij/getting-started.html

• Revert added commons-lang3 locally (for now) since it is no longer provided by the IDE - fixed #66 #67 and added missing commons-lang3 library and project files for IDEA #68
  • No .jar's checked into the repo
  • No .idea folder files checked into the repo (these will conflict with local developer settings, such as local path the SDK/JDK)
• Enable GitHub Actions CI Fix CI #6