GCS: Remove ResponseTime fields

This was part of something that should not have been merged in.  Input
shaping for the gimbal is performed within the CameraStab module.

fixes #195
Camera Stab: Implement an intput filter for attitude mode

It doesn't make sense to have the input filter for axis lock
mode since integrating is already a big low pass filter.  This
can slow the response for changes in desired attitude though.
Camera Stab: Move the Accel and Deccel time into the Camera settings

Previously this module was reusing some of the variables from the mixer
settings but since these are independent variable uses no reason to
confound them like that.
Camera Stab: Simplify the feedforward code

Use a single time constant for positive and negative acceleration
since servos aren't like motors in this regard.
Camera Stab: Only get the settings when they are changed

This is more efficient than getting it every time
Camera Stabilization: Update comments and code documentation
Camera Stab: Use the library bound function
Fixed bug that allowed board rotation settings to be erased if the six
point calibration process was canceled out of.
f4 usb: enable VBUS_SENSING so fw detects loss of connection
f4 usb: removed DCD_EP_Flush on endpoint TX
This has probably caused the problem that prevented tx after
a bus reconnection.
Freedom: Remove unused SPI DMA handlers

Making consistent with Quanton and removing these unused paths makes
it more readable.

Fixes #254
Camera Stab: Explicitly label variables with _ms

This avoids any ambiguity between using seconds, microseconds
and milliseconds through the code.
Merge pull request #226 from peabody124/response_time

Clean up the camera stabilization code
Merge pull request #262 from lilvinz/f4_usb_reconnect_fix

F4 usb reconnect fix
Merge pull request #259 from TauLabs/kenz/six_point_fix

Canceling out of six point calibration does not replace original rotation parameters