## Is your feature request related to a problem?

A user mentioned needing a feature to clone dashboards as they create the same dashboard multiple times, each for a different end-customer. Given that we are already planning on doing default / custom dashboards (#1659) we can add this functionality to facilitate dashboard creation.

## Describe the solution you'd like

Simple functionality to duplicate a dashboard.
- Add "Duplicate" button to dashboard list and clone dashboard (e.g. "Copy - AARRR").
![screenshot](https://user-images.githubusercontent.com/5864173/93866745-fce46100-fcbf-11ea-8c96-b1acfb1981d5.png)


## Describe alternatives you've considered
Re-create the dashboard manually.


## Additional context
No additional context.


#### *Thank you* for your feature request – we love each and every one!

posthog/api/test/test_dashboard.py
import json
from dateutil import parser
from django.utils import timezone
from django.utils.timezone import now
from freezegun import freeze_time
from rest_framework import status
from posthog.models import Dashboard, DashboardItem, Filter, User
from posthog.models.organization import OrganizationMembership
from posthog.test.base import APIBaseTest
from posthog.utils import generate_cache_key
class TestDashboard(APIBaseTest):