Allow network requests to span multiple TCP pkts

Incoming network requests can now span multiple TCP messages. Max upload
buffer increased to 2048. Also return layerHeight and generatedBy values
when asking for fileinfo on a gcode file. This is an interim commit that
needs cleaning up before release.
Support HTTP requests longer than TCP MSS

Changed webserver to support HTTP requests that span multiple TCP
messages. Changed upload code to to block file writes direct fro the
received message. Increased maximum upload message size. Changed
fileinfo command to report layer height and what program generated the
gcode file, if available.