PE: Add parser for .NET CLR

[kkent030315]

• Addresses issue IMAGE_DIRECTORY_ENTRY_COM_DESCRIPTOR #315

Added CLR parser implementations as proposed in the issue.

• Added .NET signature and COR20 header, storage header and metadata header parser.
  • Added MVID (GUID) and PK token (Public Key Token) parser.
• Added CLR sections parser.
• Added CLR tables parser.
  • Requires full re-implementation of IMetaDataTables where originally written in hard C++
• Added CLR imports parser.
  • Requires full re-implementation of IMetaDataImport where originally written in hard C++

[kkent030315]

Turns out that CLR imports and tables parser requires very complex implemenetations and I think it should not be implemented in goblin, it's up to consuemrs handle it in upper implementations, it at least should be enough to expose fundamental datas for that. So I am marking this as ready-for-review.