New theme.

Clean up of existing theme, implementation of a new easier to integrate layout.
Move advanced form out to it's own class

Make page title customizable through the Config system (Fixes #44)
Overhaul of module to use DocumentationManifest

This major update changes the behaviour of the docviewer module to use a cached manifest rather than on demand. This allows us to simplify the URL matching and store 'nice' URL configuration rather than altering handleAction().
Kill DocumentationService in favour of config API.

This continues on the migration to the Manifest. Instead of using calls to a `Service` now all file related lookups are done through the `DocumentationManifest`
Add an alphabetical index (Fixes #5)
Show nested sidebar menu
Fix breadcrumbs
Fixes for unit tests with the latest manifest
Add support for [CHILDREN] shortcode

This allows you to build up dynamic listing pages much better.
Header agnostic documentation.
Fix issue with Language parameter not being set

When the user accesses a page more than three levels deep.
Add DocumentationEntity::toMap() for assert compability
Unused template.
Add test for getChildrenFor and getVersions
Add additional test case for DocumentationFolder
Fix formatting for folder pages.
Add arrows to next / previous.
Add tests for getLanguage()
More more of the page to replacable includes.
FIX: Add tests and correct behaviour for next/prev