Fix license
Add support for n-grams search, fix search template

Support for n-grams enables better partial matches for auto-complete
style searches. Note, this does not provide any fuzzy search capability.

The DataField and DataConcept manager search methods take a new keyword
`partial` that, if true, will use the n-grams index.

This also fixes a silent bug that caused no data values to be included
in the search document.