when setting periodicity with master builder module should change builder's offset to avoid building on top of each other

[programmerjake]

when setting periodicity to 3, currently it sets builders to:

Builder #1 offset=0	Builder #2 offset=0	Builder #3 offset=0	moves -->
nothing builds here	all three try to build here	nothing builds here	nothing builds here	all three try to build here	nothing builds here

what I think should happen:

Builder #1 offset=0	Builder #2 offset=1	Builder #3 offset=2	moves -->
#1 builds here	#2 builds here	#3 builds here	#1 builds here	#2 builds here	#3 builds here