Making the dashboard optional

[jamiehewitt15]

Fixes #327

Changes proposed in this PR:

• Making the dashboard optional
• Dashboard still runs by default, the new env is optional

To test:

export DASHBOARD="false"
npm run build
npm run start 

Navigate to http://localhost:8000/dashboard/ and there should be no dashboard.

Now run:

export DASHBOARD="true"
npm run build
npm run start 

and the dashboard should be running at http://localhost:8000/dashboard/

[paulo-ocean]

lgtm, apart that unit test we know it fails atm

[bogdanfazakas]

lgtm, think we should merge first the PR with env-md docs and add the Dashboard there as well