make it easier to find failure/warning log messages

[pbiron]

When doing a small import it is no problem searching through the output of the log section of the Step 3 screen to find any failures/warnings. However, when doing an import with thousands of posts/terms/etc it is hard to find ouot if anything failed.

I don't have any great ideas about how to do this, but a couple of things that come to mind are:

1. allow the log section to be sortable by the Type column once the import has completed. The Tablesorter jQuery plugin would make that easy to do.
2. style warning and fail rows differently than info rows (i.e., with different background colors, yellow and red come to mind).

It would also help to add counts of failures/warnings to the "Summary" section of the Step 3 screen as well (maybe parenthesized in the Completed column, e.g., "10493/10493 (3 failures)") so that the user knows whether they should look through the log section to find the warning and fail rows.

[drzraf]

on a side note: #154