Support "load" key in arc system configuration
Support "load" key in arc system configuration

Summary: I think @nh needs this at some point?

Test Plan: Added bogus and valid "load" to system config, got warning and load respectively.

Reviewers: nh, dschleimer, btrahan

Reviewed By: dschleimer

CC: aran

Differential Revision: https://secure.phabricator.com/D2931

coursera/arcanist,kevinseelbach/arcanist,zhihu/arcanist,dguo-coursera/arcanist,jra3/arcanist,coursera/arcanist,uber/arcanist,wxstars/arcanist,jra3/arcanist,hach-que/arcanist,wxstars/arcanist,dguo-coursera/arcanist,wikimedia/phabricator-arcanist,eSpark/arcanist,wharris/arcanist,KieranHayes/arcanist,coursera/arcanist,hach-que/arcanist,Symplicity/arcanist,folsom-labs/arcanist,PageUpPeopleOrg/arcanist-patches,r4nt/arcanist,folsom-labs/arcanist,folsom-labs/arcanist,aik099/arcanist,eSpark/arcanist,calblueprint/arcanist,zhihu/arcanist,haskell-infra/arcanist,wxstars/arcanist,haskell-infra/arcanist,codelabs-ch/arcanist,wharris/arcanist,memsql/arcanist,r4nt/arcanist,sneakpeeq/arcanist,kevinseelbach/arcanist,phacility/arcanist,wikimedia/phabricator-arcanist,dguo-coursera/arcanist,sneakpeeq/arcanist,kevinseelbach/arcanist,calblueprint/arcanist,KieranHayes/arcanist,folsom-labs/arcanist,sneakpeeq/arcanist,alexmv/arcanist,fivestars/arcanist,chundongwang/arcanist,memsql/arcanist,alexmv/arcanist,julkiewicz/arcanist,PageUpPeopleOrg/arcanist-patches,Khan/arcanist,Khan/arcanist,wikimedia/phabricator-arcanist,jra3/arcanist,eSpark/arcanist,Khan/arcanist,KieranHayes/arcanist,julkiewicz/arcanist,Symplicity/arcanist,zhihu/arcanist,calblueprint/arcanist,Symplicity/arcanist,codelabs-ch/arcanist,alexmv/arcanist,fivestars/arcanist,wxstars/arcanist,julkiewicz/arcanist,memsql/arcanist,codelabs-ch/arcanist,hach-que/arcanist,aik099/arcanist,r4nt/arcanist,coursera/arcanist,julkiewicz/arcanist,KieranHayes/arcanist,alexmv/arcanist,wikimedia/phabricator-arcanist,phacility/arcanist,wharris/arcanist,sneakpeeq/arcanist,dguo-coursera/arcanist,phacility/arcanist,Symplicity/arcanist,zhihu/arcanist,haskell-infra/arcanist,PageUpPeopleOrg/arcanist-patches,chundongwang/arcanist,eSpark/arcanist,codelabs-ch/arcanist,jra3/arcanist,chundongwang/arcanist,phacility/arcanist,hach-que/arcanist,wharris/arcanist,uber/arcanist,r4nt/arcanist,calblueprint/arcanist,PageUpPeopleOrg/arcanist-patches,kevinseelbach/arcanist,phacility/arcanist,fivestars/arcanist,codelabs-ch/arcanist,uber/arcanist,uber/arcanist,haskell-infra/arcanist,Khan/arcanist,memsql/arcanist,fivestars/arcanist,aik099/arcanist,aik099/arcanist,chundongwang/arcanist