SwissArmyCase: Add clips onto case body to hold onto EmotiBit PCB

[produceconsumerobot]

I'm imagining clips that sit kitty corner next to the side strap attachment to provide easier "one clip at a time" removal and prevent sliding when used with non-stacking header.
We may wish to make the notch in the clips support either 0.047in or 0.062in PCBs for forward compatibility.