allotments - metatile alignments

Providing a new symbol (2 versions) for the global metatile alignment of landuse=allotments.
As the previous hatching pattern of 5:1 pixel (5 px colour, 1 px transparent, total 6 pixels high)
does not match a power-of-2 icon size, a 7:1 and a 3:1 pattern have been created, which 
lead to a slightly coarse or dense hatching. I'd prefer the 7:1.

Previews below for both versions. The area is here, where you have a vertical misalignment about 20m left of the scubs: http://www.openstreetmap.org/#map=17/52.52700/13.24974

Closes #643

![allot_7-1](https://cloud.githubusercontent.com/assets/8266355/3714004/b1a7a7dc-1590-11e4-9989-7b5b07449a45.png)
![allot_3-1](https://cloud.githubusercontent.com/assets/8266355/3714006/b8fc88ae-1590-11e4-96e8-18ef093ca753.png)