cqerl_ts: Rename options to cassandra_*

With another cassandra driver in the works, to simplify switching
between the two, rename options the options to have a `cassandra_'
prefix.

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
cqerl_ts: Drop cassandra_use_prepared

The non-prepared version of the ts_insert opteration was dysfunctional
to begin with, so this patch removes it. There's no point in trying to
do such a thing.

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
seestar_ts: New cassandra driver, using seestar

The advantage of Seestar is that it has better, more convenient support
for prepared statements, and we can use bindings within Cassandra
functions too.

We also switch the example config to use this new driver instead.

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>