[Patch] Query module column reordering

[ebray]

This is a patch I came up with at PyCon specifically because some of my users need it, but I think something like it could go into Trac core.

First of all it solves the problem of the poor scalability of the UI for selecting columns to display, which is pretty unusable in situations where there are something on the order of 50 custom fields (which I've seen, and it's ugly).

I also needed the ability to let users reorder the columns, which this solves. I'm sure how the Trac devs will feel about this. It replaces the 'col=' query arguments with arguments in the form 'col#=', where # is the order that that column should be displayed in. This works fine for URL query strings. But I haven't updated the TracQuery syntax to support column reordering. Other than that it seems to work fine, and includes support for non-JavaScript users.

[hyugaricdeau@…]

Some of the diffs may be from my editor removing stray whitespace, which may be annoying.