Using Spotless for formatting

[pbaumard]

• Reorganized sections since this code style is not only for Java.
• Removed format rules since they are defined by Spotless.

Note:

• related to Spotless formatting creedengo-rules-specifications#366 including the reference pom.xml with Spotless configuration.
• thousands of Open Source projects are already using Spotless, including major ones such as Apache Maven. It makes it much easier to:
  • apply the common format with mvn spotless:apply for contributors
  • check that the common format is applied in build with spotless:check goal included in pom