[1.0][Configuration] Cleanup bundle configuration.

This PR address https://github.com/liip/LiipImagineBundle/issues/287 RFC and partly https://github.com/liip/LiipImagineBundle/issues/294 RFC.

Currently I added a factory only for web path resolver. This is how you can configure it:

```yaml
liip_imagine:
    resolvers:
       # default options
       web_path:
           web_path: ~ 
    
       # with custom options
       images_web_path:
           web_path:
               web_root: foo
               cache_prefix: images/cache
```

Later you can refer to them as before:

```yaml
liip_imagine:
      filter_sets:
        thumbnail:
            cache: web_path
            filters:
                thumbnail: { size: [223, 223], mode: inset }

        images_thumbnail:
            cache: images_web_path
            filters:
                thumbnail: { size: [223, 223], mode: inset }
```