v4: Some bugs on ion-card

[mburger81]

Describe the Bug
We try to use your ion-card and sub components using alpha.7 with latest beta documentation.
We also created a demo repo https://github.com/mburger81/ionic4-tests where you can navigate to Cards menu to see bugs and simulate them.

This is what we have figured out, or we think we have figured out :)

1. You can use ion-card-subtitle before ion-card-title, but this should be a wrong usage and probably you can avoid this by using slots, right? In this case it would be independent from the order you list it in code, we found this bug on your first card example in docs https://beta.ionicframework.com/docs/api/card
2. The ion-card-header on MD should be 20px instead of 24px, right?
3. setting color attribute to ion-card-header does not have any effect, perhaps color attribute is already documented on docs but not implemented on alpha.7?

4. We are not sure how to use ACTIONS in ion-card-header, perhaps we are missing something or there is a bug, but having a look to your documentation we found this out
   • we should use ion-item in ion-header if we wan' to use buttons, wrapping ion-card-title and ion-card-subtitle in ion-label
   • if we use ion-item in ion-card-header the padding is completely different from first example, which should be the right padding

[Ritzlgrmft]

I have the same problem with <ion-card-header color="...">, using 4.0.0-beta.7.
However, it was helping to set the color attribute for the card itself: <ion-card color="...">. This changed the color of the header...

[ionitron-bot]

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