Add prototyping space

[samuk]

If we re-rerouted the trace from pin 15 we could provide some onboard prototyping space, similar to Feather

1. The area between pin 14 and pin 16 down to the 'bottom' 5v could be perforated.

2. All the pins in that bottom section 'below' 14-16 pins could have solderable pads put next to them for connecting to those pins

3. We could break out & silkscreen 3v, 5v & Gnd & I2C pins somewhere around the edge of the 'proto' section, if not already conveniently exposed by 2)

[runger1101001]

I like this idea. The manufacturing cost is 0$, but the benefit to the user is large :-)