Convert develop/packages docs to reStructuredText

[leorize]

The MediaWiki syntax used by the docs have several problems:

• Unable to have more than one paragraph per list items. This is relied upon by Bootstrapping, and BuildingPackages
• Hard wrapping can't be done globally as lists end on new line
• Heavy reliance on HTML tags, a side effect of this is that all HTML symbols has to be escaped

Markdown was considered as an alternative, but:

• Still rely on HTML tags for tables and ToC (Table of Contents). Github Flavoured Markdown solve tables, but not ToC
• ToC has to be written by hand
• -, _ has to be escaped, which renders Markdown unsuitable for the docs, namely Bootstrapping, Migration, HybridBuilds, ...
• Definition lists can't be converted without losing schematic, used by FileFormat

reStructuredText however, provides:

• Markdown-like syntax, easy to read and edit
• No reliance on HTML tags, nor could you use them within the docs
• ToC generator

The rendered rST version could be found ​here. It should be comparable to PackageManagement

Change: ​https://review.haiku-os.org/#/c/98/

[waddlesplash]

Merged in hrev51832. Thanks!