Add index.html instead of FileUploader main class

It's slightly awkward having 2 main classes in the complete project because
ony one of them can run from the command line by default. Consequently a user
cannot take the "complete" project and follow the instructions in the README
because the server cannot be run from there.

This change adds an index.html to the application so it can be driven from a
browser instead.

N.B. this sample is broken with Boot RC4 (RC3 still fine)