* http OPTIONS canonicalization:
- rename PostQueryExtractor to generic MethodQueryCanonicalizer, handles OPTIONS verb in addition to POST
- use more generic 'query' instead of 'post_query' for method-query canonicalization
- append '__pywb_method=options' to OPTIONS responses to distinguish from get in MethodQueryCanonicalizer
* method canon: also add HEAD to __pywb_method query canonicalization
- utils.io for stream/compression related utils
- utils.format for string formatting
- utils.memento for memento
- load_config -> utils.loaders.load_overlay_config
- also: use warcio.utils.to_native_str instead of utils.loaders.to_native_str
- ResAggApp -> BaseWarcServer
- AutoApp -> WarcServer
- move index related files to warcserver.index package, tests to warcserver.index.test
- move resource loading related files to warcserver.resource package, tests to warcserver.resource.test
- pywb.cdx -> pywb.warcserver.index
- split pywb.warc -> pywb.warcserver.resource or pywb.indexer (for cdx generation)
- bump to 0.51.0 for now!
- tests for pywb.warcserver should be working