Merged *next branch* into master with the following changes:

Porting ddprint to Ender5 (pro):

  * Changes for the Creality melzi board (atmega1284p based).
  * Added thermistor table for epcos 100k ntc.
  * Declared IO-pins in firmware/pins_ender3.h
  * Rework homing:
    + use feedrate and direction for homing from printerprofile.
    + Move away from nozzle after z is homed (for printers that
      home at z=0. This is to avoid scratching over the bed when
      homing X and Y.
    + Homing: added "4 point mode" for ender.
  * Added new script *thermistor_table.py* to generate thermistor
    tables (c-code).

Other changes:

  * Host: rework *getstatus* and *mon* commands.
  * Host: filament profile measurement:
    + measure2: increase printing speed with fixed
      temperature while monitoring feeder grip.
    + measure2: changes to reduce heating effect of
      heated bed, start measurement on fifth layer.
    + specify minimum grip value on commandline (instead of
      hardcoded value).
    + write measured material profile to ./mat-profile2.add.
  * Host, *removefilament* command: changed feeding
    sequence to avoid filament plug.
  * Host, Experimental: added *reconnect* command.
    To reconnect to a running printer, works after
    download is complete, but not if disconnected
    while downloading stepper data.
  * Host: Added *ddprint version* command.

  * Firmware: cleanup flowrate measurement,
    measure short moves, too.
  * Firmware: added CmdGetVersion command.
  * Firmware, Makefile: new target *make gitversion.cpp*
  * Firmware: set printer state to idle if steppers are
    disabled (cmd *disablesteppers*).
  * Firmware: Update to SdFat-1.1.4 library (USE_SD_CRC enabled).
  * Firmware: Rework mass storage erase: new commands CmdGetCardSize
    and CmdErase. Call erase before printing.
  * Firmware: Sd card init: retry up to 5 times.

  * Many smaller fixes/improvements