Add new metrics "complexity in classes" and "complexity in methods" to compute "complexity/class" and "complexity/method"

In some languages we can have a code, which is not associated with classes, but currently "complexity/class" - is a total complexity divided by number of classes, whereas should be - total complexity in classes divided by number of classes (see http://jira.sonarsource.com/browse/CPP-121 and http://jira.sonarsource.com/browse/ABAP-122). New metrics should be introduced to compute correct values. Plugin should be responsible to save values for files and Sonar to compute on other levels.