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.
* detect csv delimiter in csv rendering
fixes#7868
* make linter happy
* fix failing testcase & use ints where possible
* expose markup type to template
previously all markup had the .markdown class, which is incorrect,
as it applies markdown CSS & JS logic to CSV rendering
* fix build (missing `make css`)
* ignore quoted csv content for delimiter scoring
also fix html generation
6543
Lunny Xiao