removed sum Formula on covered statements metric

- measures should be saved for all levels (directory, project, module, file)
- the sum should not be necessary any more
- makes the two metrics more similar, a correct "sum" for the coverage value
cannot be defined as easily.

Author: MichaelZinsmaier

plugin/src/main/scala/com/buransky/plugins/scoverage/measure/ScalaMetrics.scala

@@ -53,6 +53,5 @@ object ScalaMetrics {
     .setDirection(Metric.DIRECTION_BETTER)
     .setQualitative(false)
     .setDomain(CoreMetrics.DOMAIN_SIZE)
-    .setFormula(new org.sonar.api.measures.SumChildValuesFormula(false))
     .create[java.lang.Integer]()
 }