As noted by @taratata2016 in https://github.com/MarlinFirmware/Marlin/issues/3300#issuecomment-204687275

Redo of #3268 by @jbrazio

These are salvaged from closed-PR #3216.

Closes #3245

In all these cases we want the axis to be homed. If we could have lost
some steps is secondary.

Reenables homing seperate axis with DISABLE_X / DISABLE_Y true.

copy of 406992f9dd

Also add mbl.z_offset to the EEPROM, bumping the version to V23.

Following up on #3231

PROBABLE ->PROBEABLE
This is follow-up to #3069?

Fixes for #3189

Setting a temp is still missing

Adds the parameter U to M303. If U1 is included , it will use the
PID-values from the auto-tune.

Send position updates to RH where RH can not know the end position.

For example after G28 RepetierHost assumes to be at the homing-point,
but with a servo probe we are much higher. Now the RH-software-endstops
will prevent us from going down (if activated). With this patch the
internal position of RH is updated with `current_position[]`.

SERIAL_ECHO is not very good in printing uint8_t - so cast. to int.

Add return to NOT_BUSY for M105
Replace WAIT_FOR_USER with PAUSED_FOR_USER

Add Travis test for FILAMENTCHANGEENABLE

Fix a SNAFU that should have been caught in #3012