Reformat source code with IntelliJ IDEA preset

Some of this may be slightly off but it's better than it was
Merge pull request #152 from Kobata/style-reformat

Reformat source code with IntelliJ IDEA preset
Update README.md, add CONTRIBUTING.md

Signed-off-by: Steven Downer <grinch@outlook.com>
Change the project definition so that subprojects inherit configuration.
Move the example plugin to its own project.
Add copyright header for ExamplePlugin.