use theme settings for card border

[ChristophCaina]

Is your feature request related to a problem? Please describe.
it seems, that the card does use its own settings for the card border (shadow, etc.)
it would be great, if the card would just use the settings given by the theme - to be in the same look as the other cards.

Describe the solution you'd like
the card should use the options set in the theme for shadow, border-width and radius.

Additional context