Update reprap.js

Requires RepRapFirmware-057f-dc42.bin  - available here https://github.com/dc42/RepRapFirmware/blob/duet/Release/

Home all added,
detects if setbed.g exists and adds a button if it does
upload progress popup.
Settins tab items work
Setting to use Half Z movement values e.g. 0.05 instead of 0.1 etc..
includes dc42's upload changes which achieves a file upload speed of 1.96Mb/sec.