Total refactor of Beeper

Rather than generating the full audio clip (16 pulses of 1000 samples
each) in a single go, buffer the `zero` and `one` pulses and emit them
in order.

Also add a dummy "header" pulse, to work around a problem I've had with
my circuit and/or Arduino not reading the first pulse correctly. This
goes along with a corresponding change to the arduino code (incoming in
a future commit) to detect and ignore the longer header pulse.
Tweak durations; add header pulse check

The "header" pulse is an extra-long pulse that begins transmission of
the remaining 16 pulses (generated by commit bb718dbb to the Android
SoundTest app); this header is detected and ignored (and sometimes, at
least on my hardware, it doesn't go through at all, which is OK because
it would be ignored anyway).

This ends up making my 16-bit pulse transmission from Android to Arduino
more reliable. YMMV.
Move Arduino stuff out of subdirectory
Add VirtualWire library
Add Fritzing files
Rework breadboard and PCB views

The breadboard view is a bit cleaner now; I also revised the PCB view to
closely resemble the stripboard layout used in the book. All three views
are fully routed now.
Move .apk to see if github will make a QR code

Per https://github.com/blog/665-apk-downloads-for-android-projects