Peek reipients, fetch existing messages

Read all of an e-mail accounts messages and extract all To/CC addresses
if the From was from our own account.
Then, fetch existing messages from the server and show them.

Also, I fixed two other things:
- just by chance my test failed because of an completely unrelated bug.
The bug: bcc_self messages were not marked as read if mvbox_move was set
to true.
- add some color to the test output (minor change)

python/src/deltachat/events.py

@@ -1,6 +1,7 @@
 import threading
 import time
 import re
+import os
 from queue import Queue, Empty
 
 import deltachat
@@ -48,6 +49,15 @@ class FFIEventLogger:
         if self.logid:
             locname += "-" + self.logid
         s = "{:2.2f} [{}] {}".format(elapsed, locname, message)
+
+        if os.name == "posix":
+            WARN = '\033[93m'
+            ERROR = '\033[91m'
+            ENDC = '\033[0m'
+            if message.startswith("DC_EVENT_WARNING"):
+                s = WARN + s + ENDC
+            if message.startswith("DC_EVENT_ERROR"):
+                s = ERROR + s + ENDC
         with self._loglock:
             print(s, flush=True)
 
@@ -111,6 +121,15 @@ class FFIEventTracker:
                 print("** SECUREJOINT-INVITER PROGRESS {}".format(target), self.account)
                 break
 
+    def wait_all_initial_fetches(self):
+        """Has to be called after start_io() to wait for fetch_existing_msgs to run
+        so that new messages are not mistaken for old ones:
+        - ac1 and ac2 are created
+        - ac1 sends a message to ac2
+        - ac2 is still running FetchExsistingMsgs job and thinks it's an existing, old message
+        - therefore no DC_EVENT_INCOMING_MSG is sent"""
+        self.get_info_contains("Done fetching existing messages")
+
     def wait_next_incoming_message(self):
         """ wait for and return next incoming message. """
         ev = self.get_matching("DC_EVENT_INCOMING_MSG")