Support one level of nested configs

In the config file you can now say:

    [default]
    key = value
    nested =
        subkey = 1
        other = 2

And it will be parsed as:

    {'key': 'value', 'nested': {'subkey': 1, 'other': 2}}
Add handler to override signature version based on cfg value
Merge branch 'config-sigversion' into develop

* config-sigversion:
  Add handler to override signature version based on cfg value
  Support one level of nested configs