Find a better way to set the webapp version

[Romain Baugue]

This version should be the same than the server version, which would avoid the mess that is actually required to have the correct version commited.

Ideas of the bat:

• have the version be set in the index.html file, and override it on-the-fly in the server endpoint
• find a way to set it using go:generate

[Romain Baugue]

Solved by bef5ea5.