* commands to support introduction
* agent messages / envelopes to support introductions
* introductions and invitations table; insert record with random unique ID
* store class methods and types for introductions
* process INTRO and ACPT commands for connection introductions
* fix tests: add MonadFail constraint, remove OK response to JOIN
* process agent messages for introductions
* ICON notification when introduction is completed
* replace multiway if with case
* correction
* support random connection IDs
* save additional connection fields, refactor create connection funcs
* refactor
* refactor
* test duplex connection with random IDs
* store methods for introductions
* test introduction
* fix parsing of CON agent message
* test introduction with random connection IDs
* broadcast with random connection and broadcast IDs
* clean up sql
Evgeny Poberezkin