Handle empty states properly

We want to handle empty states on each view properly.

The particular handling method is up to the implementor, just follow the current design.
Dashboard view, when the user has no strategy selected.
Dashboard view, when the portfolio indicators are not applicable for the user (requires API change too).
Portfolio view, when the user has no portfolio or no item on the current portfolio.
Watchlist view when the user has no watchlist or no item on the current watchlist.

horvathmarton / stock-buddy-dashboard