Install statistics endpoint #11

Added install endpoint, filter, codecs. Updated dummy data script to
insert install records by a configurable flag (which defaults to 0).
Added URL parameters + database fields names for install fields.

Change-Id: Ieedc18a738a343f9c34b514bfa1dae69c69d9c7d
Signed-off-by: Martin Lowe <martin.lowe@eclipse-foundation.org>