Add script to handle upload of dengue data. Add some geo data.

[trvrb]

The dengue scripts are good, but some things need changing before this can be merged:

• source-data/geo_synonyms.tsv has had its formatting messed up with spaces converted to tabs: https://github.com/nextstrain/fauna/pull/40/files#diff-8611720e569f2560f622006c368b7214R11
• vdb/denv_upload.py should be vdb/dengue_upload.py for consistency
• changes to vdb/parse.py should be unstaged. I know these are fixes, but better to have more atomic pull requests
• source-data/geo_regions.tsv should keep the sorting by region (2nd column) like it is currently
• source-data/denv_strain_name_fix.tsv should be source-data/dengue_strain_name_fix.tsv for consistency

[trvrb]

The easiest thing will be probably be to start a new branch (say dengue or dengue_merge) from master and rebase clean changes on top of this new branch.