Enhance node status feature in overview and nodes

This commit uses the new parameter with_status from nedap/pypuppetdb#18

Node status is now shown as text with the additional information of
failed/succeded events, unreported time

The statistics on Overview now show the *number of nodes*
that have status failed/changed/unreported
nodes view filter now works with new status attribute
change sorting of the overview node status in javascript
Merge pull request #28 from digitalmediacenter/improve-nodestatus

Enhance node status feature in overview and nodes