* adaptive rewrite improvements:
- Add 'application/vnd.apple.mpegurl' as HLS type in rules.yaml and default_rewriter.py
- Support setting max resolution and max bandwidth to choose, defaults to 480x854 and 200000 respectively
- LiveWebLoader provides a get_custom_metadata for specifying WARC-JSON-Metadata header, per mime type (TODO: support customization via rules)
- When filtering, first limiting by resolution (if set), then by bandwidth (if set), otherwise default to max bandwidth
- Max resoluton/max bandwidth stored in WARC record under WARC-JSON-Metadata as 'adaptive_max_resolution' and 'adaptive_max_bandwidth' to ensure replayability. If absent, choose absolute max in manifest to be backwards compatible
- Add sample HLS and DASH manifests for testing, with and without max resolution/bandwidth settings.
- rewrite headers after content to ensure content-length/content-encoding rewritten if content modified
- header rewriter: remove proxyrewriter, set default rule to 'prefix' or 'keep' if url rewriting or not
- set is_content_rw if record.content_stream(), assume content is modified
- add BufferedRewriter as base for dash, hls, amf rewriting which processes the full stream
- should_rw_content() determines if should attempt content rewriting
- support banner-only insert mode: added HTMLInsertOnlyRewriter, enable if no custom JS rules
- test: enable banner-only test mode
- rewriter interface accepts RewriteInfo instance
- add StreamingRewriter adapter wraps html, regex rewriters to support rewriting streaming text from general rewriter interface
- add RewriteDASH, RewriteHLS as (non-streaming) rewriters. Need to read contents into buffer (for now)
- add RewriteAMF experimental AMF rewriter
- general rewriting system in BaseContentRewriter, default rewriters configured in DefaultRewriter
- tests: disable banner-only test as not currently support banner only (for now)
