added option for setting cache in datasets module
added option for setting cache in datasets module

joergdietrich/astropy,DougBurke/astropy,StuartLittlefair/astropy,StuartLittlefair/astropy,dhomeier/astropy,tbabej/astropy,pllim/astropy,pllim/astropy,joergdietrich/astropy,saimn/astropy,dhomeier/astropy,AustereCuriosity/astropy,bsipocz/astropy,stargaser/astropy,lpsinger/astropy,MSeifert04/astropy,pllim/astropy,joergdietrich/astropy,pllim/astropy,funbaker/astropy,larrybradley/astropy,tbabej/astropy,lpsinger/astropy,lpsinger/astropy,DougBurke/astropy,tbabej/astropy,stargaser/astropy,stargaser/astropy,kelle/astropy,lpsinger/astropy,kelle/astropy,funbaker/astropy,lpsinger/astropy,AustereCuriosity/astropy,kelle/astropy,mhvk/astropy,saimn/astropy,larrybradley/astropy,StuartLittlefair/astropy,mhvk/astropy,larrybradley/astropy,joergdietrich/astropy,aleksandr-bakanov/astropy,DougBurke/astropy,astropy/astropy,astropy/astropy,tbabej/astropy,stargaser/astropy,saimn/astropy,funbaker/astropy,dhomeier/astropy,dhomeier/astropy,DougBurke/astropy,StuartLittlefair/astropy,tbabej/astropy,pllim/astropy,aleksandr-bakanov/astropy,AustereCuriosity/astropy,astropy/astropy,aleksandr-bakanov/astropy,saimn/astropy,StuartLittlefair/astropy,aleksandr-bakanov/astropy,funbaker/astropy,kelle/astropy,bsipocz/astropy,mhvk/astropy,astropy/astropy,kelle/astropy,bsipocz/astropy,joergdietrich/astropy,saimn/astropy,MSeifert04/astropy,MSeifert04/astropy,AustereCuriosity/astropy,larrybradley/astropy,dhomeier/astropy,MSeifert04/astropy,AustereCuriosity/astropy,astropy/astropy,bsipocz/astropy,mhvk/astropy,larrybradley/astropy,mhvk/astropy