Implements request #14320 The rendering of CSV files does match the diff style.
* Moved CSV logic into base package.
* Added method to create a tabular diff.
* Added CSV compare context.
* Added CSV diff template.
* Use new table style in CSV markup.
* Added file size limit for CSV rendering.
* Display CSV parser errors in diff.
* Lazy read single file.
* Lazy read rows for full diff.
* Added unit tests for various CSV changes.
Richard Mahn
Lunny Xiao