Navigation support

[lovelydinosaur]

Version 2.0.dev4

Navigation support

This pull request adds very rudimentary initial navigation support, although note that API (well, template context) on this isn't finalised.

Specifically this adds:

• Multipage support.
• Updates the default theme to support.
• Updates the homepage theme to support.
• Includes licensing.
• Version bump to 2.0.dev4.

This PR includes more changes than it should, though I'll allow it to stand. We'll improve on process as we go.

Note that the template context will probably change here... {{ site.nav }} seems more obvious / consistent?

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Actions for future process improvements...

• Changeling.
• Test & deployment workflows.
• Minimal coherent changes & neat review / sign-off.

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Actions for future nav work here...

We can get some decent initial support without any config items. We should probably try to fill that out as much as possible before dealing with config based nav.

• Use same title casing / renaming as GitHub markdown file conventions.
• Strip leading digits / hyphens / underscores???
• Add next / previous support.

Future work related to config based navigation...

• Actually reading from config.

Future work related to nested navigation...

Can some of this be supported with auto-nav based on directory names?

• children
• breadcrumbs
• siblings (elders/generation)