Completion, hover and deprecations from the vocabulary #102

Part of ComlineProject/core#219, proposal ComlineProject/docs#162 (rollout stage 5). Blocked on ComlineProject/core#220.

• Completion and hover from the vocabulary:
  • encodings and handshakes (with their facts);
  • guarantees, in accept_unverified and granular @unverified keys;
  • annotations, settings keys, and fact values.
• Deprecated names and aliases offer the canonical spelling as a quick fix.
• Remove the hand-kept names, for example the guarantee strings in src/acceptance.rs and the encoding sets in analysis/comline_toml.rs.