fix: remove fileblocks statistics

This patch accomplishes a couple of things. First, it removes the
fileblocks stats. These stats are an implementation detail and should
not be exposed to the user. Secondly, the queries are impossible to do
in cassandra.

This patch also fixes some Cassandra aggregation queries that are not
supported but were missed because our Cassandra driver is mocked with
sqlite (which does allow aggregation functions).
test: dictionary args for mock_cassandra

This patch adds dictionary support to our mock_cassandra framework.
feat: use dicts instead of positional tuples

This patch changes the cassandra queries to use dictionary (aka 'named')
arguments for queries. This is to prevent errors from creeping in in the
future due to positional arguments getting out of alignment.
chore: pep8

Fixes pep8 violations
Merge pull request #86 from painterjd/fix_cassandra_vault_stats

Fix cassandra vault stats, use dicts instead of tuples.