Improvements to web functionality

These changes allow much greater functionality via the web interface, in conjunction with Matt's web interface at https://github.com/iamburny/OrmerodWebControl. Direct printing over Ethernet now works, and the file upload speed is increased more than ten-fold to 1.82Mb/min. The firmware tracks whether each axis has been homed, and this status is reported via the web interface. After the X and Y axes have been homed, movements on these axes are limited to the bed dimensions. When uploading files to the SD card, comments are preserved so that the stored file is a true copy of the original. The code has been tidied up to eliminate most Eclipse code analysis warnings.