Code Clean-up: Use parameter instead of global

In quick_accel_sensor, instead of using the target variable that
is passed, we are using the global ackReply variable. That is now
fixed, making the code more modular.
Changing accel settle time + add documentation

The accelermeter should wait for around 6ms before being read. I have
changed the code to wait for around 8ms, as well as added documentation to
that number so the people can understand where it came from.
Adding new sensor files
Adding the SPI driver for the accelerometer device.

Adding two levels of files to suppor the accelerometer. First, we
added the digital_accel_sensor.c and .h files to provide the pin
connections and the interface to use with the accelerometer. Then
we added the code to allow the moo to actually interface with the
board.
Merge branch 'master' of github.com:spqr/umassmoo into moo_12_master
Moving pin specification from digital_accel_sensor.h to board.h, because they are specific to the board
Adding test script
Updating files with new debug testgin
Adding schematics for Moo 1.2

Schematics include gerber files, for future board manufacturing and
assembly, as well as PDF of schematic and bill of materials.
Digital Accel works sometimes without FET

With these code changes, I'm able to get the moo to report back,
with some accuracy, the accelerometer data. If the FET is attached
at this point, we get accurate readings 100% of the time. However,
once we detach the FET, not so much. I theorize that it's because
the accelerometer is losing power, and we aren't giving it power
again, but I could be wrong. According to the spec, you need to give
5ms for the device to reach standby mode, and then 40ms for the first
reading. That is a LONG time. I'm thinking that we just keep the
device in powered on at all times. I probably need to power in the
device just incase it of a power lose in the read_sensor function,
but I'm going to move on to interrupt based reading of the sensor.
Enabling SPI interrupt based transactions

This code allows for the SPI bus that communciates with the digital
accelerometer to be interrupt driven. This allows for a much faster
tag rate and (hopefully) less power usage. THERE IS CURRENTLY A BUG,
1 times in 4 or so, we get into a state where the digital accelerometer
never updates it's values. We just get the same data back over and over
again. I need to look into that. It's probably something to do with
timer a.
Fixing bug where board sometimes doesn't update

Every so often, when we powered on the board, we would get into a
state where it wouldn't update any information. The cause, we
believe, was the 5ms that it takes to start the board. We now delay
for 5ms using noops while we wait for the accelermeter to turn on.
This causes some issues where, when we lose power, we now take at
leasst 5ms to turn on. We will look at that later, but for now we
are looking into sleeping for those 5 ms.
Adding sleep_ms function that allows the device to sleep for n milliseconds if we want too. We are using this for turning on the accelerometer, as it can take up to 5ms to turn on.
Merge branch 'master' into moo_12_master
Adding temp_sensor from master to this branch of code so that we can use the temperature sensor on the moo 1.2s
Merge branch 'master' into moo_12_master
Adding simple sensor to the moo for simple testing

The "simple sensor" allows us to get the fastest available tag
rate without having to worry about the sensor interface (for
example, the SPI bus with the digital accelerometer) causing
delays in the system that my be in some way harming the RFID
signal analysis, or causing a timeout.
Adding new code to deal with interrupts from the digital accelerometer
Removing sleep_ms function

There seems to be a problem with TimerB, in that we can "miss" it's
interrupt and then be stuck in sleeping land forever. Therefore, I've
removed the sleep_ms code from the moo, and have added the
intrinsic "__delay_cycles" to busy wait instead. Because I don't plan
on supporting this code for much longer, I think that's a fair
solution to the problem.
Switching moo version in my_moo.h