dw_dev | "introduction" bugzilla keyword

As the "introduction" keyword happened while I was out on my honeymoon and I wasn't in the loop, it figures that I come back and I am not a big fan of it. So, let's just use "effort-minor" keyword which is already there and doesn't have a great definition.

Henceforth, if you want to indicate that a bug is "small/easy and a good bug for new developers", then please mark it with "effort-minor". I will be removing the "introduction" keyword from Bugzilla later this weekend, so people have time to go through and swap the keywords if they care.

I didn't get anybody objecting to this plan when I asked about it a few weeks ago nor when I mentioned it on IRC, so this seems reasonable and sane.

Thanks!