Sending a daily issue automatically

tl;dr A BrowserView that creates and send an issue per day

Sending a daily issue automatically
-----------------------------------

It includes `@@daily-issue` BrowserView, in order to create and send daily issues, using the default template and
default criteria. For using it, you just need to configure your crontab (or clock server) to send a `POST` on `@@daily-issue` view. Eg:
```
#Sends a newsletter, from Mon to Fri, at 0:00AM
0 0 * * 1-5 curl -X POST http://user:passwd@example.org/mynewsletter/@@daily-issue
```

`@@daily-issue` returns a HTTP status code indicating what just happened (you can also test it with a GET, instead). 

```
--------------------------------------------------------------
| Method/Precondition | Not yet sent | Empty  | Already Sent |
--------------------------------------------------------------
| GET                 | 100          | 204    |  200         |
--------------------------------------------------------------
| POST                | 200          | 204    |  409         |
--------------------------------------------------------------
```