Ability to insert an RFCXML table

[ajeanmahoney]

The user should be able to insert RFCXML code for a table that can then be populated with content. The user should be able to place a cursor in the XML where they want the code to appear, then select attributes of a table such as header and footer and number of rows and columns, and then generate the table code.

The functionality is currently provided by https://www.rapidtables.com/web/tools/html-table-generator.html (with some manual cleanup of the output).

[ajeanmahoney]

Also see #39.