Cache manifest handling

[markfinger]

#20 laid a lot of the groundwork and proved the worth (it's annoying having to warm up and maintain a build server)

Workflow

• user runs webpack command
• system builds the config files which have been listed
• writes the output to a manifest file

[markfinger]

This deviates from the previous attempts as we're now heavily dependent on context which is passed to the config files.

Needs support for

• manifest keys which reflect the config file and the context
• contexts can be specified in settings
  • for each config file
  • multiple contexts for a file can be generated

Conf should end up looking something like

{
    # ...
    'CONFIG_DIRS': (
        os.path.join('...', '...'),
    ),
    'MANIFEST': {
        # This builds and caches the output for the default context
        'styles_config.js': None,
        # This builds and caches the output for each context
        'react_component_config.js': (
            {
                # context ...
            },
            {
                # context ...
            },
        ),
        # ...
    },
    'USE_MANIFEST': True,
    'MANIFEST_FILE': 'manifest.json',
}

[markfinger]

Fixed in latest