Axsuarez/4.12 cherry picks (microsoft#1540) * Add TabEntityContext to init.py (microsoft#1538) * axelsrz/export-dialogs-memory (microsoft#1539) Co-authored-by: Eric Dahlvang <erdahlva@microsoft.com>

Invoke with expected replies (microsoft#1427) 

Add end_on_invalid_message and fix timeout issue (microsoft#1339) * Add end_on_invalid_message and fix timeout issue * fixing pylint Co-authored-by: Axel Suarez <axsuarez@microsoft.com>

SkillDialog activity type handling updates (microsoft#1057) 

Axsuarez/qna model fix (microsoft#868) 

use get_access_token in signed_session, to ensure the Authorization t… …oken in the session is not expired (microsoft#602)

Merge pull request microsoft#536 from microsoft/eric/fixGetTeamsConne… …ctorClient Teams connector client creation cleanup

Merge pull request microsoft#370 from microsoft/axsuarez/fix-appinsig… …hts-setup Adding processor as exported package

Initial template for echo bot (microsoft#351) 

Add missing flask package (microsoft#300) (microsoft#301)