add basic display of errors tabs in status.
add basic overview tab to for status view.
disable status-tab-links if count is zero

Usually a count of zero reflects that there
is nothing to see inside the tab.

Also changes the way css-classes are determined by
outsourcing this to its own method.
use merge to generate states-count hash

This has the benefit of preserving the inherent
ordering of the STATES array.
use overview as a default status tab.