Fix error handling in DE (#294)

- Replaced `JSON.stringify(error)` with `error.message`
- Created `ErrorHandlingUtils` and moved all error logging actions in there

src/Explorer/Graph/GraphExplorerComponent/GremlinClient.ts

@@ -57,9 +57,9 @@ export class GremlinClient {
           this.flushResult(result.requestId);
         }
       },
-      failureCallback: (result: Result, error: string) => {
+      failureCallback: (result: Result, error: any) => {
         if (typeof error !== "string") {
-          error = JSON.stringify(error);
+          error = error.message;
         }
 
         const requestId = result.requestId;