update meta data

[jcayouette]

Description

This PR adds meta descriptions for doc-hpc main.

meta descriptions for files of the following DOCTYPE:

• <!DOCTYPE appendix
• <!DOCTYPE chapter
• <!DOCTYPE preface

The following doctypes were skipped:

<!DOCTYPE sect1
<!DOCTYPE sect2 
<!DOCTYPE sect3 
<!DOCTYPE sect4 
<!DOCTYPE sect5 
<!DOCTYPE book 
<!DOCTYPE article 
<!DOCTYPE set 

Placing of meta descriptions and 'its' namespace

# Placed inside the <info> element. 

<meta name="description" its:translate="yes">...</meta>  

Added the namespace:

xmlns:its="http://www.w3.org/2005/11/its"

See the meta description html report in project root for detailed changes