UndocumentedApi : Javadoc {@inheritDoc} tag support

Part of [SONARJAVA-70](https://jira.codehaus.org/browse/SONARJAVA-70) : Javadoc [{@inheritDoc}](http://docs.oracle.com/javase/7/docs/technotes/tools/windows/javadoc.html#inheritDoc) tag support = considered as consistent (because it is not since [SONARJAVA-265](https://jira.codehaus.org/browse/SONARJAVA-265)). 
Useful for Java 1.4 / 1.5 (with interface inheritance)

Activation by rule property (false by default).

ML thread : [ squid:UndocumentedApi support inheritDoc Javadoc or not ? ](http://sonarqube.15.x6.nabble.com/squid-UndocumentedApi-support-inheritDoc-Javadoc-or-not-td5027286.html)

Sorry for space format diff ... I can fix.