DocViewer always renders first tab ignoring shouldShow

[timroes]

Every docView can implement a shouldShow method, to tell if it should be visible for a specific document or not. Unfortunately doc_viewer.js will always set the first tab in order as active, without checking if it is actually visible for that document.

We need to fix this, and maybe switch to regular templating in that directive instead of doing manual templating via a function in case there is no reason for that anymore.