InheritanceFree: skip inheritance from abstract classes

[nikialeksey]

inheritance - there is one problem: abstract classes. I don't like to use abstract classes, but I think nothing wrong with them. And in this inspections I would like to add filter option skipAbstractClasses, which would skip inheritance from abstract classes, and architecture of java-plugin needs to be changed, because we need to accumulate project information at first, and then use it in our inspections.