Update Surrey Air Survey bounds

Part of #42
Merge pull request #52 from pnorman/surrey_air_bounds

Update Surrey Air Survey bounds
Add GB country codes to GB sources
Move GB imagery into the UK folder
Merge pull request #53 from pnorman/gb_country

Gb country
Added second orthophoto of Erlangen from 2011
Merge pull request #56 from osmlab/patch-1

Added second orthophoto of Erlangen from 2011