Merging views engine

Hello ! 
I rebased PR #391.
This PR doesn't include the possibility to use external commands (rescheduled, ask, ...). I will add this feature in other PR when this one will be merged.

@matthieucan  could you confirm or not this ?
In `adagios/status/templates/custom_views/widgets/link_host.html`
The current line :
```
<a href="{% url "status.views.detail" %}?host_name={{ value }}&backend={{ line.backend }}">{{ line|hash:col_name }}</a>
```
Should be
```
<a href="{% url "status.views.detail" %}?host_name={{ line|hash:col_name }}&backend={{ line.backend }}">{{ line|hash:col_name }}</a>
```

Thanks !