Value of lineId for Violation is not deterministic

Violation.lineId might be null and 0 - seems that both values indicates that violation attached to file, but not to a concrete line. Which leads to misunderstandings, because method Violation.getLineId returns original value.

• setter must log a warning if value<1. It will throw an exception in future releases
• getter must return null or value>=1
• add the methods "boolean hasLineId()" to both org.sonar.api.rules.Violation and org.sonar.wsclient.services.Violation
• violation web service does return the lineId field only if value is set (>=1)
• javadoc should be improved to describe convention