Dataset submission detalis

resolves #54 
I suggest splitting this into more functions:

1) takes the time and returns the string
```clojure
(defn date->days-ago-str
    ...
    (let [interval ...
        (interval->days-ago-str interval)))
```
2) takes and interval and returns a string for the amount of time
```clojure
(defn interval->days-ago-str
    ...
    (let [interval-in-secs...]
        ))
3) a function to pluralize and concat, this one's generic so maybe use it in `templates.datasets` also
```clojure
(defn pluralized-number
    [number kind]
    (str number (plural kind)))
```