Sort imports and remove unused imports

[tbroyer]

The Formatter class won't sort imports or remove unused imports. This can be done using the ImportOrderer and RemoveUnusedImports classes respectively.

See google/google-java-format#96 which adds this as a default behavior in the Formatter class.

(note that java -jar google-java-format-1.3-all-deps.jar uses FormatFileCallable instead of directly calling the Formatter; FormatFileCallable sort and cleans up imports in addition to formatting the code; actually, this is probably what this plugin should use too)

[jbduncan]

For Spotless, we effectively call the following lines one after another.

String source = ...;
String formatted = new Formatter().formatSource(...);
formatted = RemoveUnusedImports.removeUnusedImports(formatted);
formatted = ImportOrderer.reorderImports(formatted);

Using FormatFileCallable would be tricky if not impossible without reflection AFAICT, because it requires an instance of CommandLineOptions, which is a default-visibility class.

[jbduncan]

On a somewhat different note, I'm interested in seeing this issue resolved as well, as it would make implementing jrtom/jung#86 easier for us.

[pastjean]

Fixed by #13

[jbduncan]

Great to see that this issue is resolved now. Thank you very much @pastjean and @therealppa. 👍