update_fix: move topology ops to their own moduel
update_fix: elminiate per-switch policy cache

The code for maintaining the specialized policy for each switch was
entangled in all the flowtable update code. Remove it for now so the
update code can be refactored in a sensible way. If there's a problem
with packet_in performance, then the cache can be reintroduced in a more
principled way.
update_fix: move best effort update to new module, refactor
update_fix: more specific args for compute_internal_table

All that compute_internal_table uses the `t` argument for is to compute
the internal ports of the topology. Just pass those in instead.
update_fix: more specific args for compute_edge_table

All that compute_edge_table uses the `t` argument for is to compute
the internal ports of the topology. Just pass those in instead.
update_fix: move move table construction to Update module
update_fix: Remove unnecessary uses of Monitor.try_with

These instances of Monitor.try_with are unnecesasry, as the exceptions
are rethrown and nobody is listening to the error stream.
update_fix: bring up switch with versioned flowtable

Fixes issue where new switches entering the network were not getting
versioned flowtables.
update_fix: reoganize code into modules
Merge pull request #306 from frenetic-lang/update_fix

Fix consistent updates: install versioned flowtable on new switches