ATTRIB/ATTDEF proper processing

[vagran]

It should be investigated how to properly handle ATTRIB/ATTDEF entities.

Here is one piece of information.

As I see, they are not always rendered by Autodesk viewer, but are listed in block attributes instead:

[dotoritos-kim]

#58 Added logic to select the correct layer and block. Please take a look.

[dotoritos-kim]

#58 Changed the logic a bit. All insert entities are put into an array and sorted groupBy. And Match the handle like that to find the insert.