feature(dashboards): custom views

[ryangjchandler]

This PR adds a couple of new methods to the NebulaDashboard class:

• NebulaDashboard::display() - similar to NebulaPage::display(), is the parent method used for calling the underlying render method.

• NebulaDashboard::render() - used to change the view that a dashboard returns, allowing for custom views.

• NebulaDashboard::displayMetrics() - used to render the metrics, using the default view provided by Nebula.

These changes will allow developers to change the view that is used for the dashboard, greatly improving the customisation, whilst still being able to render the default metrics view.

[Cannonb4ll]

Nice work @ryangjchandler, as always 💪

[ryangjchandler]

Nice work @ryangjchandler, as always 💪

Oh sh it you! <3