fixed Global/WorldBank-Statistics_v2012 files

Hi @jules32 ,

I only manually fixed the field names of these files:

- [rgn_wb_uem_2014a.csv](https://github.com/OHI-Science/ohiprep/blob/master/Global/WorldBank-Statistics_v2012/data/rgn_wb_uem_2014a.csv): value to percent
- [rgn_wb_tlf_2014a.csv](https://github.com/OHI-Science/ohiprep/blob/master/Global/WorldBank-Statistics_v2012/data/rgn_wb_tlf_2014a.csv): value to count

Probably a good idea to update [data_prep.R](https://github.com/OHI-Science/ohiprep/blob/master/Global/WorldBank-Statistics_v2012/data_prep.R) too.