first version of a makefile. This is based on the makefile produced by avr studio, but sanitized so we can easily change tool paths, include dirs etc.

Any further changes to the project should also make changes to the makefile in paralell.

The makedep.mk has not been modified and can be copied directly.
flexible directory layout
makefile puts obj/dependency (*.o/*.d) files in OBJ_DIR subdir (defaults tp "tmp")
final files go in OUTPUT_DIR, defaults to "final"
At present, these directories must exist before the build (e.g. the calling shell script.)
Source dir can be specified.

This shold allow a matrix build to operate from the same source, putting obj and output files in separate locations.
updates for diy-shield. RotaryEncoder interrupts need sorting out to match the pins.
fixes for diy shield. Rotary encoder doesn't compile yet.
moved BREWPI_SHIELD_xxx definitions into brewpi.h since they are used by the config, so need to appear before them.
Fixed file path separators in makefile.
change case of makefile
complete makefile lowercase rename
fixes for linux build.

- case sensitive #includes
- removed .exe extensions in makefile
- fixed repeated output dir for cleaning .lss file
Merge branch 'feature/dynaconfig' of https://github.com/BrewPi/brewpi-avr into feature/dynaconfig
Merge branch 'feature/dynaconfig' of github.com:m-mcgowan/brewpi-avr into feature/dynaconfig
commented makefile (a bit)
support for BOARD and SHIELD makefile params
factored out compiler defines
additional space prevented line continuation character from working in DEFINES
Merge branch 'feature/dynaconfig' of github.com:m-mcgowan/brewpi-avr into feature/dynaconfig