[vector-api] Avoid 404 in hosted examples

Currently the hosted examples generate a warning:
```
Failed to load resource: the server responded with a status of 404 (Not Found) http://ol3js.org/en/vector-api/css/ol.css
```
This is because the path to `../css/ol.css` is embedded in the HTML examples. This file does not exist when the examples are hosted. This PR fixes this by always loading the CSS via `loader.js` (in hosted mode `bin/loader_hosted_examples.js` is used instead). It also removes some trailing whitespace.