Start using humanized dates in some prominent places

While we have the infrastructure upstream since sometime, we haven't made use of it on master. (SUSE Manager is already carrying these patches)

As a guideline I used: dates like "last login" "last checking" are displayed with the "from" style
See http://momentjs.com/docs/#/displaying/fromnow/
Other dates are shown with the calendar style, which changes depending how far are you from the date.
See http://momentjs.com/docs/#/displaying/calendar-time
All dates of course have a tooltip with the full localized non-human date plus a ISO date in the time HTML5 element.

There are much more places where this can be used, these are only a few prominent ones.

![c77334de-d5f1-11e3-9565-094e011d5ee6](https://cloud.githubusercontent.com/assets/15332/3038653/7c76a3a0-e0d0-11e3-84d2-26c6fa8306bc.png)

![ced5b31e-d5f1-11e3-800a-75174c531043](https://cloud.githubusercontent.com/assets/15332/3038656/8694533c-e0d0-11e3-846d-7ddaca233b11.png)

![d0b3b03c-d5f1-11e3-9f58-f08dcc3f2f3c](https://cloud.githubusercontent.com/assets/15332/3038660/9317bf0e-e0d0-11e3-8cbe-5c118455b227.png)