histogram: dateformat implementation unification and improments

This is a improved of the date formats  based in intervals used in histogram

Now the formats of the histogram are:

less 1d: `HH:mm<br>MM-DD`  (16:01 01-08)
less 1w: `YYYY-MM-DD<br>dddd` (2014-01-08)
less 1m: `YYYY-MM-DD<br>Wo [week]`  (2014-01-08 1st week)
less 1y: `YYYY-MM-DD<br>MMMM` (2014-01-08 January)

BTW i made a merge of the code used in the ticker and the label.

![screen shot 2014-01-08 at 16 08 03](https://f.cloud.github.com/assets/1573114/1869118/bf6284da-7876-11e3-9b89-da1cdc45881c.png)