Code cleanup


Entry.java:
In applyModification(), extracted methods applyModificationToObjectclass() and applyModificationToNonObjectclass().
In hasUserAttribute() and hasOperationalAttribute(), extracted method hasAttribute()
Used Attribute.isReal() to explicit code + merged if statements.


Attribute.java:
Added isReal() -> !isVirtual().

AbstractAttribute.java:
Implemented isReal().
In equals() extracted method valuesEqual().
In hasAllOptions() and optionsEqual(), extracted method hasAllOptions0().