Add configuration for throws clause indentation

Checkstyle reports hundreds of error for code like this:
public void someMethodWithLongSignatureSoThrowsMovesToNextLine()
  throws SomeException

The earliest report about that is date 2008: http://en.it-usenet.org/thread/13413/346

https://github.com/checkstyle/checkstyle/pull/80 adds throwsIndent configuration parameter and finally resolves the issue.