A working API generator for our pelican-datastore plugin. Is WIP but:

* Generates a static JSON API endpoint for each dataset in the datastore
* Supports excluding a dataset
* Supports generating filtered endpoints based on dataset key (e.g.: all entries for 2013)
Support multiple formats on API (now CSV and JSON). Cleanup code.
Small docs changes on custom jinja filters
Fixes to templates. Adding a download page.
Ignore CLI build directories.
Merge branch 'master' of github.com:okfn/opendataindex

Conflicts:
	.gitignore
Add coverage for tests.
Document the API in the README
Fix typo.
Add the datastore_assets plugin, which generates public assets for download from the datastore. Update the download page with archive and API downloads.
Small fixes.
Fix typo in template.