Leanback: fix fading mask and make ImageCardView up to spec

No longer need a fading mask per ux.

Adjusted padding, size, color up to date.

remove redundant FrameLayout.

Remove the code that change visibility based on content.
All the cards on same row should have same height, regardless
their content.  Haven't yet decided how to provide a two
textviews customization.

b/21662705

Change-Id: I8c435bb12a3ee8344f463a4975a2af4c5f14f516
6 files changed