This patch eliminates the global configuration variables `opt` and `g`, making
all functions and class instances locally configurable. Configuration data is
passed to functions and constructors via the `cfg` parameter and made available
to methods in `self.cfg`.
Local configuration free from dependence on the command line will enable the
creation of multiple, independently configured instances of MMGen’s data
objects within a single process.
Potential applications include testing (tracking wallets configured to interact
with spawned processes, for example) and the use of MMGen as a library for
other projects.
This patch completes most of the work required to enable the API. The full
implementation will appear in a forthcoming commit.
