Prepare all SQLite databases locally

[stitam]

Related to issues #77, #82, #83.

This PR implements conversion to SQLite locally within taxizedb. Orginal code for conversion to SQLite:

• COL: https://github.com/sckott/col-sql
• GBIF: https://github.com/sckott/gbif-backbone-sql
• TPL: https://github.com/sckott/tpl-sqlite

These were re-implemented within the respective db_download_*() functions.

The URL for COL seemed to point to GBIF so I replaced the URL with a new one.

The URL for WFO did not work because of an expired certificate. The new Zenodo URL works properly.

[stitam]

With all the failing tests it was hard for me to tell whether my GBIF implementation was working properly, so I decided to combine multiple issues in the same PR and fix them together.

Note that until 2019 COL used integer taxon IDs (e.g. 3960765) but since 2020 COL uses character IDs (e.g. C66T4). This impacted a number of examples and tests so these were also updated.