stepper motion with acceleration/deceleration
permanently enable laser idle current (for now)
fix typo
add double buffer for line data (with automatic switching)
work on host software
switch index diode polarity (seems to improve timing jitter for now)
make number of scans per line and automatic stepping configurable
add command line arguments to put_image.py
add laser driver hardware
changed DMA flag names according to newer libopencm3 version
updates flash.c to newer libopencm3 APIs
updates usb.c to newer libopencm3 API