SQL-like Filter Operations

[seba-1511]

The idea is to execute SQL-like queries on the database of JSON files, for a given experiment.

From the programmatic API, this means that you can get a list of results based on queries similar to what you'd get with SQL queries. We can provide some sane default functions, but the best is to have a filter function like: filter(lambda result: result['field_a'] > 32).

For the web-interface, this would be a search-bar with the same kind of syntax as for VisualScience.