feat(rxStatusColumn): Add support for coloured status columns

This provides `rx-status-header` and `rx-status-column` attribute
directives, used to modify `<th>` and `<td>` elements for the purpose
of showing coloured statuses in one column of a table.

You can define mappings to go from your own internal status values
to the four currently provided by the framework.

Closes #688
As an alternative to storing the associate between font-awesome and the status type in the JS, I believe it would be possible to store this in the Less file:

```
@import (reference) "font-awesome.css"; 
.status-icon {
    .fa();
    .fa-lg();
}
.status-icon .status-ERROR {
    .fa-exclamation-triangle();
}
```

I'm betting that import isn't correct, but that's the general idea.