Add new string function
Revert settings.h

It wasn't a good idea to merge this with board.h
Forgot to change board.h
Fix board::cnv2volt() to board::cnv_to_volt()

Additionally change the place of "using namespace aery" below to #defines.
Fix serial_port_clsdrv::printf

vsnprintf() may return the number of characters which would have been
written to the final string if enough space had been available.
Fix typo in namespace
Refix the serial_port_clsdrv::printf()
Minor changes

- Include <aery32/all.h> in board.h
- Update docblock for serial_port::printf()
Formal changes
Formal changes to examples/serial_port_class_driver.cpp
Add Makefile feature to exclude source files
Remove extra whitespace :P
Bump to version 0.6.1
Merge branch 'master' into 0.6