Memory: investigate compression

Investigate using in-memory compression to store "large" string objects.

In particular, note text and other/unknown line chunks.

Useful links:

https://blogs.msdn.microsoft.com/shacorn/2014/11/12/optimizing-memory-footprint-compression-in-net-4-5/
https://madskristensen.net/blog/compress-and-decompress-strings-in-c/
https://github.com/jaime-olivares/zipstorer
https://dzone.com/articles/memory-cache-implementation-c

Start by reviewing the linked articles and the ZipStorer project to compare in-memory compression approaches for C#. Identify where large string objects, note text, and other or unknown line chunks are stored in YAGP. Done should include a documented approach and evidence that compression improves memory usage without unacceptable parsing or access costs.

Written by the indexing model from the issue text.