Fsr

Hey Johann:

I've added two bits of functionality to Marlin/your FSR code.  Feel free to take all, partial or none:

- I added a define called FSR_ANALOG_READ.

If defined, the code remains unchanged (reads from thermistor).  If undefined, it uses the Z_MIN to detect if the bed height has been hit or not.  

For me this is essential as I'm using John Socha's board to send a digital signal (LOW) when hit, and I want to (one day) use my thermistor for the bed as intended.

- I've started separating Configuration.h into MyConfiguration.h and Configuration.h.

I find it a bit cleaner - MyConfiguration.h is .gitignored, so people can have their own settings there, but not get stomped over by other people.  MyConfiguration.h.example can show people how things can be done, and Configuration.h can be left as the #define logic processor it currently is.

Let me know if you have any questions, suggestions, or violent responses to this. :)

Cheers,

-e-