* Always use selective imports
* Use `imported` for one-off uses of a module
* Delete unused imports
* Reorder imports to start of the function

…ption` type

And use range algorithms in its implementation.

…tion headings

With this change, links of the form
`basics/delegates#anonymous-functions-lambdas` are no longer rejected. Instead,
they're accepted and clicking on them leads to the browser navigating to the
right page and highlighting the specific heading.

This is done by:
* Validating: stripping off the fragment part before checking of the given file exists
* Adjusting the AngularJS (ng1) routing - enabling HTML5 mode (i.e. disabling
  the default "hashbang" mode) and disabling client-side URL rewriting
* Adding a CSS rule to highlight the heading that the URL is linking to

Needed for compatibility with vibe.d 0.96.0.

…name` to get an actual `string`

Needed for compatibility with vibe.d 0.96.0.