Removed the DIA classes and the cod associated with it. Introduced a PdbReaderFactory that decides with PdbReader to use (full or portable). Introduced a PdbReader interface that abstracts the differences between full pdb (Uses ISymUnmanaged classes to read the pdb) and portable pdb (uses Reflection MetadataReader).

test/TestingAbstractions/TestAppWithFullPdbs/ClassForFullPdbs.cs

@@ -0,0 +1,13 @@
+namespace TestAppWithFullPdbs
+{
+    public class ClassForFullPdbs
+    {
+        public void TestMethodForFullPdbs()
+        {
+        }
+        
+        public void AnotherTestMethodForFullPdbs()
+        {
+        }
+    }
+}