Feature/last updated data

An API handler have been added to get brief info about which the `n` last updated documents in the databases are. This is called and displayed on the front page of the web app to provide a quick view of what metadata have been active recently.

In this case, times refer to the modification times of documents.

![Ska rmavbild 2013-04-29 kl 14 38 35](https://f.cloud.github.com/assets/668803/438470/34ff121e-b0ca-11e2-9e32-c9a744a6e112.png)