Coq 8.7 does not support notation patterns.

This implements a depth first execution of chain actions with support
for deploying contracts from contracts and calling into other contracts
recursively. To support these things, contracts need to exhibit a
bijection of their types from and to OakValue. This machinery is modeled
with type classes. Then, use this to avoid having to store strongly
typed contracts anywhere; instead, a contract can be converted to a
WeakContract instance (using a coercion). The WeakContract verifies that
messages and states serialize/deserialize correctly and then passes
everything along to the strongly typed contract under the hood.

Previously a contract could not store ChainAction's in its state because
of universe inconsistencies.

This reverts commit eda9cff7.
Let's just give up on Coq 8.6.

Containers needs to be updated for the dev build as Coq does not use
Camlp5 anymore.

This allows heterogenous treament of Oak types and values.

* Add =? operator for addresses
* Add rudimentary block chain info (block number, needed by Congress.v)