Add separate content element for material-card

[Frank3K]

In the current build (d5d7e8d) there is a white margin around the image in a material-card. This margin is not conform the design spec.

Previously, this white margin was not present; it is a result of the changes in f33185f.

See also #247.

[ajoslin]

OK, to fix this we'll have to add a separate content element for the card itself.

[ajoslin]

Will fix default padding inside all cards seems too small (not entirely certain) in #347.

[mzbyszynski]

👍

[mzbyszynski]

HI @ajoslin, Not sure if you saw these comments, but I wanted to make sure you are aware that this last commit removed the outer margin and hence paper effect from md-card, which I don't think was your intent. Here's a plunkr that shows the problem. Should be an easy enough fix...

[ajoslin]

Ah, right. I'll put it back.

[Frank3K]

The fix unfortunately re-introduced an old probleem, see #247.