[Tilesathome] t at h server updates

[Christopher Schmidt]

1. The user requesting a tileset is now recorded...
2. Which let me find out that some clients were requesting a huge number
   of requests, which let me find out that...
3. The t at h server has not been correctly handling re-requests since
   mid-August. This is now fixed.

Some clients are still requesting a huge number of requests and
returning them as broken tiles, or not returning them at all. user 
'jaiku' is a case of the latter.

In order to handle this, I've added a column to the users database:
'disabled'. This allows you to mark a user as 'disabled': if this is the
case, the t at h client will get a "We have no work for you" response.
Anyone with access to the database can update this flag from true to
false or false to true, and it is displayed on
http://tah.openstreetmap.org/Credits/ .

robfitz and jrreid both have clients which are shoving lots of
Rerequests on empty tiles: robfitz's client reports "TooBig" (Which
isn't in the client in SVN), and jrreid reports 'BadSVG'.

jaiku is currently disabled -- the others are not, but should probably
see if their clients are doing okay.

To jaiku: If you can ping me sometime, so we can watch what your client
is doing, we can turn your client back on and watch it. If anyone knows
who this is and can pass this along, that would be good. (I have no clue
if the user in question is on this list.)

Regards,
-- 
Christopher Schmidt
MetaCarta