To allow deployment to different chains but using the same deployment
scripts, this commit introduces a basic `DeploymentConfig` which can be
extended as necessary in each project.
There's a few things that should be considered:
- `activeNetworkConfig` will be initialized via the constructor, at
which point it is know what `block.chainid` is
- To add new configuration settings, extend `NetworkConfig`
- To add a new config for a different chain, extend the `if/else` block
in the constructor so that it creates a `NetworkConfig` for the chain
in question
