refactors webapi and client lib

client/drng.go

go.mod

go.sum

pluginmgr/webapi/plugins.go

plugins/webapi/broadcastData/plugin.go

plugins/webapi/drng/collectiveBeacon/handler.go

plugins/webapi/drng/info/committee/handler.go

plugins/webapi/drng/info/randomness/handler.go

plugins/webapi/drng/plugin.go