Describe for LIS structures

[ErlendHaa]

In DLIS all metadata and logical/physical file objects have a describe() method that prints a human readable summary of the object. This has turned out to be really useful as the content of files tend to differ greatly. describes is an fast and easy way to get an overview of the file content.

We should aim to implement describe for in the LIS submodule to. Relevant Classes are:

• LogicalFile
• PhysicalFile
• DataFormatSpec
• InformationRecords
• All the fixed record types
• ...