data: parsing and saving inheritance

This change parses inheritance in CxxParser and saves them as EDGE_INHERITANCE in the Storage's graph. Tests for correct
inheritance recognition were added to CxxParserTestSuite.

fortune cookie message = If you continually give, you will continually have.

bin/app/data/src/header.h

@@ -2,3 +2,6 @@ int main();
 void foo();
 int sum(int a, int b);
 int diff(int a, int b);
+
+class A {};
+class B : public A {};