GitLab

* Replacing the contents of `README.md` with `RELEASE_NOTES.txt` (converted to markdown) and deleting `RELEASE_NOTES.txt`.
* Adding additional instructions in maintenance directory, including specific instructions on maintaining the documentation (`DOCUMENTATION_INSTRUCTIONS.md`) and doing releases (`RELEASE_INSTRUCTIONS.md`)
* Creating a stylesheet (`ttb.xsl`) for MATLAB-generated pages and updating the style file (`ttb.css`) for static pages. This fixed the problem of the extra scroll bar inside the MATLAB help browser (min-height of the html from 100% to 90%).
* Deleted several redundant or unneeded web pages: `getting_started.html`, `bibtex.html`, `helpscreen.PNG`
* Reorganized and updated `index.html`
* Updating `helptoc.xml`.
* Adding navigation to all HTML pages.
* Removing any references to the old `bibtex.html` file and making reference styles more uniform.
* Capitalizing page titles.
* Adding footers to all manually-created pages.
* Re-running publish for all MATLAB-created pages, which also adds a banner to those pages.
* Updated instructions in `CONTRIBUTION_GUIDE.md` to indicate how to use the stylesheet
* Updated calls to `rng(_number_)` to be `rng('default')`
* Fixed small errors in documentation, like spelling errors
* Deleted the unneeded file: `doc/helptoc_template.xml`

Fixes issue #13