• introduce a configuration file /etc/moonfire-nvr.toml; you will need
  to create one when upgrading.
• bump minimum Rust version from 1.53 to 1.56.
• fix #187:
  incompatibility with cameras that (incorrectly) omit the SDP origin line.
• fix #182: error
  on upgrade from schema 6 to schema 7 when a camera's onvif_host is empty.
• API bugfix: in the GET /api/ response, include ext streams if
  configured.
• fix #184:
  Moonfire NVR would stop recording on a camera that hit the live555 stale
  file descriptor bug, rather than waiting for the stale session to expire.
• progress on #70:
  shrink the binary from 154 MiB to 70 MiB by reducing debugging information.