V1.30-preview

Fixes #2: Piwebcam: Enable overriding of camera settings

How to override camera settings:

Connect to the ttyACM device and issue
/usr/bin/v4l2-ctl -L | less

Then, put the SD card back into the computer, 
create a file called camera.txt in /boot and put all parameters
you want to be overridden, for example:

auto_exposure_bias=15

You can also remount the boot partition read/write to edit it
on-line:

mount -o remount,rw /boot