Current monitoring on CC3D
First cut of allowing a 3POS switch on AUX3 to change rc rate.

rcRate is decreased when low, increased when HIGH and no change when the
switch is in the middle.

The rcRate ticks up/down at 0.01 every 500ms if the switch is left on.

If using a momentary switch and if you can toggle the switch between
middle and low or middle and high more frequently than 500ms then the
rate will be increased accordingly.  Similar to how a keyboard repeat
behaves.
Make the adjustment controls more sensitive by using a smaller 3POS
switch deadzone.
Makefile improvement
- root must be assigned when declared - with :=
- add autodependecy generation
Merge branch 'ledvinap-feature-makefile'
Merge pull request #131 from ledvinap/bugfix-trivial

Trivial changes
Merge pull request #132 from ledvinap/bugfix-targets

quick fix
Update target identifier for MassiveF3.

Target identifiers should 4 characters long.
Merge pull request #133 from ledvinap/feature-nvic

Feature nvic
Merge pull request #128 from Pierre-A/cc3d-updates-1

Current monitoring on CC3D
Re-instate the original softserial workaround.

This will be investigated further after the softserial changes are
merged in.
Fix rc_controls_unittest to use midrc.
Update adjustmentConfig to include the adjustment timeout.
Use adjustment index rather than function to track state.
Seperate adjustment configuration from adjustment state.  Rename 'step'
parameter to 'delta' applying the adjustment.  Configure adjustment
states based on adjustment configuration for AUX3 and AUX4.
First cut of API documentation.

Note this is already out of date for current master branch.
update some comment typos in sensors/acceleration.c
Beep when adjustments are made. (very short = adjust downwards, short =
adjust upwards).
Extract range definition so it can be reused.
Add cli command to configure adjustment ranges.

e.g. `adjrange 0 0 1700 2100 1 2`

set adjustment range 0, which applies to aux channel 0 (aux1) when range
is between 1700 and 2100 then apply function 1 (rc rate) to aux channel
2 (aux3)