Cleanups to tilemill backbone FS backend.
Cleanups to tilemill backbone FS backend.

MappingKat/tilemill,Zhao-Qi/tilemill,MappingKat/tilemill,fxtentacle/tilemill,mbrukman/tilemill,isaacs/tilemill,Teino1978-Corp/Teino1978-Corp-tilemill,Zhao-Qi/tilemill,fxtentacle/tilemill,MappingKat/tilemill,tizzybec/tilemill,Zhao-Qi/tilemill,makinacorpus/tilemill,MappingKat/tilemill,florianf/tileoven,Teino1978-Corp/Teino1978-Corp-tilemill,Zhao-Qi/tilemill,tilemill-project/tilemill,florianf/tileoven,nyimbi/tilemill,tizzybec/tilemill,paulovieira/tilemill-clima,paulovieira/tilemill-clima,isaacs/tilemill,makinacorpus/tilemill,nyimbi/tilemill,mbrukman/tilemill,tilemill-project/tilemill,fxtentacle/tilemill,tizzybec/tilemill,nyimbi/tilemill,Zhao-Qi/tilemill,mbrukman/tilemill,nyimbi/tilemill,Teino1978-Corp/Teino1978-Corp-tilemill,paulovieira/tilemill-clima,MappingKat/tilemill,tilemill-project/tilemill,paulovieira/tilemill-clima,florianf/tileoven,isaacs/tilemill,tizzybec/tilemill,Teino1978-Corp/Teino1978-Corp-tilemill,paulovieira/tilemill-clima,mbrukman/tilemill,Teino1978-Corp/Teino1978-Corp-tilemill,fxtentacle/tilemill,tizzybec/tilemill,fxtentacle/tilemill,nyimbi/tilemill,mbrukman/tilemill