new grid: us_dc_neighborhoods

[rexarski]

Grid data:

row,col,code,name
1,2, 4, Ward 4
2,1, 3, Ward 3
2,2, 1, Ward 1
2,3, 5, Ward 5
3,2, 2, Ward 2
3,3, 6, Ward 6
3,4, 7, Ward 7
4,3, 8, Ward 8

[hafen]

Added in https://github.com/hafen/grid-designer/pull/8