NPPacw function and data cleaning July 2014

I wrote new code for cleaning census data. This is not a function, you
need to run the data through it step by step. I re-wrote the code for
the NPPacw function. Allometric equations remain the same, just added
Chave 2014.
Merge branch 'master' of https://github.com/OxfordEcosystemsLab/GEMcarbon.R