Writer Html/Pdf Support RTL Alignment of Table

[oleibman]

Fix #1104, which went stale over 6 years ago, and is now reopened. This PR addresses the alignment of the table, not alignment of text. Support is added for the following:

• Html. Full support.
• Mpdf. Full support, except that, when mixed LTR and RTL worksheets are output, all tables will be on the left of the page (but will be properly aligned).
• Tcpdf. Full support when all worksheets being output are RTL; no support when mixed LTR and RTL worksheets are output.
• Dompdf. No support.

This is:

• a bugfix
• a new feature
• refactoring
• additional unit tests

Checklist:

• Changes are covered by unit tests
  • Changes are covered by existing unit tests
  • New unit tests have been added
• Code style is respected
• Commit message explains why the change is made (see https://github.com/erlang/otp/wiki/Writing-good-commit-messages)
• CHANGELOG.md contains a short summary of the change and a link to the pull request if applicable
• Documentation is updated as necessary