Group similar resource cards/tiles into 'stacks'

[skorsch]

We would like to group resource cards/tiles into stacks instead of having them spread across the page as they are at the time of writing this. We want the following:

• When the stack is clicked, it expands the cards within it (could make them appear in a grid over top of the page and make the background darker similar to Updated Add Resource procedure #185 )
• Some sort of grouping logic (see sub-issue Logic for grouping cards #190)
• number to indicate group size when non-expanded
• Some sort of visual indicator that there is a stack of cards. Perhaps vaguely resembling:
  

Requires:

• Represent multiple cards as one special multi-card #188
• Create multi-card expansion animation and layout #189
• Logic for grouping cards #190
• Visual indicator for multi-card #191