Generalize function types in 'HashedDocuments'
Move 'Compression' to 'Occurrences.Compression'
Move 'CompressedDocument' to 'Document.Compression'
Remove --enable-tests in Makefile - use test target
Rename HashedDocuments to HashedDocTable
Add 'cabal.sandbox.config' to .gitignore
Remove unnecessary DocId functions
Cleanup and comments