some fixes and ideas from mEDI_S

hi James Sweet,

i send u a smal patch wat add a canel of calc without a full crew
so we have never bad circles, 50% crew circles in tankrange.xc from emty tanks and it lower the writes on crew switches ;)

i add now patch 2 "add spotting_limit option to old configs (lower userstress)"
some user have many problems with the old config (login hangs) i think this is usefull 

patch 3 fix the crew and component change bug

best regards

mEDI