This adds initial support for an sqlite database that is shared across
multiple tasks of a single SBY file and that can track the status of
individual properties.
The amount of information tracked in the database is currently quite
minimal and depends on the engine and options used. This can be
incrementally extended in the future.
The ways in which the information in the database can be queries is even
more limited for this initial version, consisting of a single '--status'
option which lists all properties and their status.
The goal of this is to make sure that all backend flows are compatible
and we can map between them, so that e.g. the aiger model can be used to
minimize a counterexample trace produced by smtbmc. Reducing the parts
that differ per backend (including parts that receive different input
depending on the used backend) also makes testing more effective as the
common parts are easier to cover.
