Etag headers are wrong

[ptitFicus]

Etag header dates are wrong (it indicates the 1st January 2010).

I think it's cause by a warning at build indicated that there is an unknown build option (Ignored unknown package option FixedTimestamp(XXXX)).

I think it's a play issue, maybe cause by high (1.9) sbt version, however this would need more investigations.

Fixing this will allow to change "no-cache,must-revalidate,no-store" options for index.html to max-age=0, which would allow browser to reuse it even if Izanami server is down.