Show current config and source using arc set-config --show
Show current config and source using arc set-config --show

Summary:
`arc set-config --show` only show the user config
It would be better to contain local/global/system config

Test Plan: set config by local/global/system/user/project, and check the result of `arc set-config --show`

Reviewers: #blessed_reviewers, epriestley

Reviewed By: epriestley

CC: epriestley, aran

Differential Revision: https://secure.phabricator.com/D7851

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