Added config reload and test.

Moved to Maven instead of Gradle.
Using proper project structure and package structure.

Can be found (already updated) here:
https://bitbucket.org/l2jserver/l2j-server-cli/

JDK11, we recommend OpenJDK for both Linux and Windows.
Updating Bitbutcket Pipeline OpenJDK11.
Updating Gradle Wrapper to 5.1.1.

JMockit from 1.34 to 1.35

Moving all files to main folder.
Using Gradle to define, manage dependecies and build the project.
Upgraded Gradle wrapper.