fixes #54. Adds woe_label sql functions and updates readme with new rank

* Adds new rank (6) for woe_label names from Natural Earth.
* Includes two SQL INSERT functions that add the names to the synonyms table depending on the shape of the string in woe_label

**These functions should be reviewed to check ignored rows due to iso3_adm0 mismatch. There's a new issue for this.**

Closes #54