Move all non-core extensions to separate folder (as described in CPE creation flow document)

CPEs/proposed/CPE2 - In-band account login.md

@@ -1,4 +1,4 @@
-# Account login by username
+# CPE#2 - In-band account login
 
 ## Introduction
 

CPEs/proposed/CPE3 - In-band account registration.md

@@ -1,4 +1,4 @@
-# Account registration
+# CPE#3 - In-band account registration
 
 ## Introduction
 

CPEs/proposed/CPE4 - Basic chats.md

@@ -1,9 +1,11 @@
-# Basic chats
+# CPE#4 - Basic chats
 
 ## 1. Introduction
 
 This extension is intended for organizing chats between some entities.
 
+`// TODO describe about events`
+
 ## 2. Requirements
 
 - Exchanging text messages

protocol-spec/basic-request-ratelimit.md

@@ -2,7 +2,7 @@
 
 ## Introduction
 
-This extension is intended to limit the number of requests from clients per unit of time. It is based on Protocol Errors extension.
+This core extension is intended to limit the number of requests from clients per unit of time.
 
 ## Message type identifiers