Support avrdude and fuses configuration via menuconfig. Add 'program' and 'fuses' makefile targets.

_Motivation:_ Being lazy and too old to remember all the avrdude options I sorely missed OpenMCPs 'program' and 'fuses' makefile targets. This one adds them to e6.

* configure avrdude options and fuse values via menuconfig
* searches and uses avrdude executable found in path
* uses avrdude -c ? to read and create the choice list of supported programmers
* supports commonly used options via menuconfig input fields and choices
* allows for arbitray avrdude options via menuconfig
* fuse configuration using hex values from menuconfig
* minimal invasive implementation using included files 

![avrdude_pr](https://f.cloud.github.com/assets/3242114/784576/877aea90-ea68-11e2-9f99-9a1078a0621c.png)

_Missing things:_
* more sensible defaults for all the default MCU fuse values

:+1: