Global code ovehaul - remove CAS and other, add 15 minute greet check

- Remove CAS, as it no longer works for us
- Remove other checks
- Implement 15 minute greet timeout check
- Fix chat logos
- Ditch thirdparty logger, use stdlib log facility wrapper for logging

vendor/github.com/NicoNex/echotron/v3/webapp.go

@@ -53,5 +53,5 @@ func (a API) AnswerWebAppQuery(webAppQueryID string, result InlineQueryResult) (
 
 	vals.Set("web_app_query_id", webAppQueryID)
 	vals.Set("result", string(resultJson))
-	return res, client.get(a.base, "answerWebAppQuery", vals, &res)
+	return res, a.lclient.get(a.base, "answerWebAppQuery", vals, &res)
 }