Merge turtle-formatter project into owl-cli

[atextor]

For a while the, owl-cli and turtle-formatter projects have been existing as separate projects. However, they are more closely related than originally anticipated from both a user's view and a developer's view:

• owl-cli's write command basically just wraps turtle-formatter functionality. There is a (almost) 1:1 relationship between turtle-formatter settings and write options.
• Users of turtle-formatter have explicitly asked how to use it from the command-line, so the project's readme even points to owl-cli.
• It's difficult to have a well-structured documentation that covers formatting functionality with API and command line usage.

Therefore, it makes sense to maintain both as one project with one documentation.
However, it must remain possible both to use owl-cli as a standalone tool and use turtle-formatter as a Java library.

1. Switch build to Maven #19
2. Make turtle-formatter a separate Maven module in this repo
3. Configure build to enable releasing modules to Maven Central
4. Update turtle-formatter documentation to point here and archive project