[JENKINS-23888] Add query parameter support for filtering errors based on new, resolved or unchanged

- New optional "states" parameter added to cppcheckResult/source.all page.
- It's a comma separated filter with states to include to the output (e.g. "?states=new,solved").
Merge pull request #21 from mixalturek/master

[JENKINS-23888] Add query parameter support for filtering errors based o...