'analyze' module now has tests.

As always, had to be refactored to allow for meaningful testing. The
closer you get to functional programming, the easier it is for write
meaningful tests - though I can't say clearly that oo is hard to test in
itself, but it definitely encourages types of coding which are hard to
test.
Issue #24

Change names of the 'test' and 'stats' indices. Allowing for more
flexible configuration - the name of the index into which test data is
loaded is now controlled by the config.json file ('name_index' field)
and the name of the 'stats' index is now determined by the
esbench.STATS_INDEX_NAME global variable.
Issue #23

The stats index is now a 1/0 (as opposed to the default 5/5).
Cleanup of stats index delete code.