Site download ameriflux

@mdietze @jam2767 @bcow @ankurdesai 
Initial version of web frontend that can download and convert files. I have managed to run this successfully, however there are still some issues:
- not using convert.input so nothing is written to database (can you look at this Josh?)
- some sites don't work, create invalid nc file after met2cf.Ameriflux, not sure why
- no gapfilling for CO2 yet