[TASK] Add support for image persistence

During LaTeX to HTML conversion to system can create some image, for
figure, formulas, ... Now theses images are persisted correctly, replaced
by a link to the correct asset and used the ConvertUris TS2 object to build
link during rendering.
[TASK] Use custom ht4latex configuration to produce cleaner HTML code

- Remove empty paragraph
- Remove default value for source property
- Add attributes support for the Latex TS2 object