Improve FormatWorkerAction diagnostics

[realdadfish]

Right now if there is a compilation problem in one of the linted / formatted Kotlin files, kotlinter just outputs

> There was a failure while executing work items
   > A failure occurred while executing org.jmailen.gradle.kotlinter.tasks.format.FormatWorkerAction
      > format worker execution error

It would be cool if this could directly point to the file in question that triggered the error and eventually include the actual upstream exception message.

[jeremymailen]

Good suggestion