Merge pull request #215 from wolfmanjm/upstreamedge

Upstreamedge
make pwm frequency configurable in temperaturecontrol ( allows for SSR heated beds )
Setting the I and D values needs to be scaled by the sample time.
Whenever I and D are set they are now scaled appropriately
Merge pull request #216 from wolfmanjm/fix/pid

Fix/pid
Fix mbed build on Windows machines with Cygwin

I had fixed this awhile ago in the core gcc4mbed makefiles but it
somehow got missed in the makefile used specifically for building the
mbed SDK library in Smoothie.  This fix makes sure that GNU make uses
the Windows Command Prompt instead of the Cygwin bash shell.  Without
this change, you could see errors like:
    /usr/bin/sh: copy: command not found
when building on a Windows machine.
Make PID work like arduino pid library and more like Marlin
Fix Clear watch screen on glcd
Allow auto pid to use full power
Merge pull request #219 from wolfmanjm/fix/pid2

Fix/pid2
add example pid control settings