Add fast document read

[vkbo]

Summary:

This PR adds an alternative and efficient way to read the text of a document when all that is needed is the text content with the meta data stripped. The reader is added as a static method in the NWDocument class, and a wrapper function is added to the NWStorage class.

Related Issue(s):

Reviewer's Checklist:

• The header of all files contain a reference to the repository license
• The overall test coverage is increased or remains the same as before
• All tests are passing
• All flake8 checks are passing and the style guide is followed
• Documentation (as docstrings) is complete and understandable
• Only files that have been actively changed are committed