Fix problem matchers for the test task in VS Code (#358)

Since "npm test" runs both TS Compiler and tslint, the output can
contain compilation and linting errors.

This commit is configuring problem matchers for the "run all tests" task
to correctly pick up errors reported by tsc and tslint and list them
in "problems" window.

Note: the tslint5 problem matcher is contributed by the VSCode extension
vscode-tslint (maintained by Microsoft).

.vscode/tasks.json

@@ -105,6 +105,7 @@
         "test",
         "-s"
       ],
+      "problemMatcher": ["$tsc", "$tslint5"],
       "isTestCommand": true
     },
     // running example-codehub tests

package.json

@@ -31,8 +31,8 @@
     "coverage": "open coverage/index.html",
     "lint": "tslint -c tslint.full.json --project tsconfig.json --type-check",
     "lint:fix": "npm run lint -- --fix",
-    "clean": "lerna run clean",
-    "build": "lerna run build",
+    "clean": "lerna run --loglevel=silent clean",
+    "build": "lerna run --loglevel=silent build",
     "pretest": "npm run build",
     "test": "nyc mocha --opts test/mocha.opts \"packages/*/test/**/*.ts\"",
     "posttest": "npm run lint"