Expose tracker2 tables and columns to views

First pass. This just gives you the basic tables and columns with views core's default handlers for everything.

I think we're going to need a couple of slightly fancy handlers for the equivalent of views core's "uid_touch" argument and filter, but that should be pretty easy.

However, that brings up the question of how you want the files laid out. Do you just want everything in the root, or do you want a "views" subdirectory for tracker2.views.inc and the handler .inc files?

Added handlers for the "uid_touch" argument and filter. tracker2 just swaps out the default handlers from views core for this, since it can always do a better job than the core views handlers. Given that we've now got a collection of views-related files, moved things into a views subdir.

This is all we need for #921210: Fix performance of "My issues", so this is now ready for serious review. I'm happy to commit this (so CVS blame will point to me in case of any trouble down the road).

By request from nnewton, now with a custom filter handler so that we end up with "tracker2_user.published = 1" instead of "tracker2_user.published <> 0" in the WHERE.

Fixed the UID filter in a few important ways now that I'm actually testing all the other issue views. ;)

At drumm's suggestion, I went ahead and committed this. I committed #4 to HEAD, branched the views directory for DRUPAL-6--1, and committed the hunk for tracker2.module to DRUPAL-6--1.

If there are any followup issues about this views support, feel free to ping me about them. I'm not necessarily going to watch the queue and actively co-maintain this module now, but I'm totally happy to deal with any fallout from this change.

Cheers,
-Derek