Build Tool Updates

[vkbo]

This PR:

• Updates and cleans up the Build Novel Project tool.
• Adds controls for new features, like line height and replacing Unicode characters with HTML entities.
• Removes the markdown export code from the ToHtml class as it now belongs in ToMarkdown.
• Applies line height and text margins to the HTML format as well. These were added for the ODT export.
• Rewrites the way replacing characters, mainly for HTML export, is handled. This includes a new Unicode to HTML map in the constants module.