Remove unused 'tileOrigin' code from TileCache layer

[euzuro]

seems to me like 'tileOrigin' is not used. Let's remove it.

[euzuro]

...or perhaps (as suggested by cr5) we actually *do* need that 'tileOrigin' and should instead investigate actually using it.

[tschaub]

I think I put it there because I wanted TC to have a configurable tileOrigin - or perhaps it already does. Maybe it was because I wanted OL to have a configurable tileOrigin. Anyway, I think tileOrigin is a good idea. Whether or not it belongs in this class, I can't say right now. Since it is there, and I'm trying to shorten my list of responsibilities, I'm going to close this unless it gets other feedback in a day or two.

[euzuro]

Mass ticket move out of 2.7 in preparation for a release plan.

If you are actively working on this task, and think that you can help this ticket to get finished and closed by September 1, please move it back to 2.7.

[crschmidt]

(In [8930]) "Remove unused 'tileOrigin' code from TileCache layer", (Closes #1076). Though the idea behind this is good, having the code here and unused is not the right thing to do. (See #1302) for a better attempt at what this should actually be. The reason this code exists is almost certainly a carggocult from Layer.TMS, which *does* have a tileOrigin, and I'm pretty sure tschaub started by copying from that. r=me, though it's mostly just docs.