Ward/paragraph escapes

This pull request adds code to escape < and & in Paragraph text.
Paragraph if further enhanced to convert to an HTML plugin upon shift-double-click.

This pull request also adds logic for reverting a page to an earlier version.
This could be useful for undoing unwanted HTML plugins made with the above mechanism.
One retrieves the wanted revision from the Journal then forks that version to the origin.

Forking can be confusing when prior versions also appear in the lineup.
This is especially confusing when the now obsolete version is more complete.

This pull request includes the commit from #70.