* create first-class citizen entities CxxReportIssue and CxxReportLocation (1:n)
  (CxxReportIssue::equals() allows clear distinguishing if issue was processed already)

* CppcheckParserV2: better implementation for primary and secondary locations

* CxxReportSensor: increase issues-per-module counter only once per CxxReportIssue,
                   increase issues-per-file counter only once per affected file

TODO (?): tests for CxxReportIssue and CxxReportLocation
TODO (?): use the new function CxxReportSensor::saveUniqueViolation(SensorContext, CxxReportIssue)