feat: display last error when definition/config load fails

Contains a breaking internal API change to `errActions.newThrownErr`, which will require a MINOR version bump. Swagger-Editor does not depend on the old usage style.

src/core/utils.js

@@ -126,15 +126,6 @@ export function systemThunkMiddleware(getSystem) {
   }
 }
 
-export const errorLog = getSystem => () => next => action => {
-  try{
-    next( action )
-  }
-  catch( e ) {
-    getSystem().errActions.newThrownErr( e, action )
-  }
-}
-
 export function defaultStatusCode ( responses ) {
   let codes = responses.keySeq()
   return codes.contains(DEFAULT_REPONSE_KEY) ? DEFAULT_REPONSE_KEY : codes.filter( key => (key+"")[0] === "2").sort().first()