Exclude kotlin files for Checkstyle, PMD and Findbugs

[mr-archano]

As mentioned by @rock3r we don't want to run the built-in static analysis tools (Checkstyle, PMD, FindBugs) on Kotlin files as we have dedicated tools for them.
To streamline the usage of the plugin we could just add default exclude rules to each of the tools above.

[rock3r]

They should technically not run already on pure Kotlin projects as they don't have the java plugin, but we are not covering "mixed" cases where a module has both Kotlin and Java, in that the plugins will run and trigger on all the Kotlin files.

[tasomaniac]

This should also be closed. Can you check @rock3r ?

[rock3r]

Yeah should be ok