fixed duplicates in FAO-Commodities and in `name_to_rgn_id()` (OHI-Science/ohicore#34)

Renamed `cbind_rgn()` to `name_to_rgn_id()` (in src/R/ohi_clean_fxns.R), since major overhaul of duplicate handling. Now the function drops the original `fld_name` and returns `rgn_id` with any duplicates collapsed by `collapse_fxn`. For instance with the FAO-Commodities, the following duplicates were collapsed:

```
                         rgn_id
  country                  73 140 186 209 244
    China, Hong Kong SAR    0   0   0 180   0  # China to be summed?
    China, Macao SAR        0   0   0 144   0  # China to be summed?
    Martinique              0  36   0   0   0  # Guadeloupe | Martinique => Guadeloupe and Martinique region
    Serbia and Montenegro   0   0  36   0   0  # Serbia | Montenegro => Serbia and Montenegro region
    Un. Sov. Soc. Rep.     36   0   0   0   0  # Un. Sov. Soc. Rep. > Russian Federation => Russia
```

Other fixes:
- Dropped from Netherlands Antilles expansion since already in data:
  + Aruba
  + Curacao
- Added to src/LookupTables/rgn_eez_v2013a_synonyms.csv:
  + Cabo Verde (ohi_region 41)
  + Ethiopia PDR (landlocked)
Merge pull request #42 from bbest/master

fixed duplicates in FAO-Commodities and in `name_to_rgn_id()`