Project: mulestudio
Issue STUDIO-4922: Mel autocompletion should avoid adding quotes when identifiers have valid characters 
add variables with names: "foo", "foo1","foo 1" and "foo+a" when autocompletion from "flowVars." should autocomplete: flowVars.foo flowVars.foo1 flowVars.'foo 1' flowVars.'foo+a'
Story points: 34