Trial restructuring content to leave `index.html` as landing page

[IanMayo]

The current index.html is our index.ditamap root page, and coverpage.html is a child of that.

The standard model for browsable content is for index.html to be the first page opened.

Trial this.

UPDATE: this can't be done by file-naming, or through any properties. The only way I can think of is for a post-processing (python?) phase that does this

• rename index.html to regions.html
• go through the whole folder, process every .html file to replace any instances of index.html with regions.html
• rename home.html to index.html

[IanMayo]

Fixed through introducing welcome page