Unable to change flags for messages not in the current mailbox

[octo]

If LogicMail attempts to change IMAP flags for a message not in the currently selected (at the IMAP layer) mailbox, the operation will fail.

Here is one way to reproduce the issue:

1. Select a mailbox other than the INBOX
2. Open a message
3. Wait for just over 5 minutes, to ensure that LogicMail's connection thread switches back to IDLEing on the INBOX. (can be verified through packet sniffing)
4. Reply/Forward the current message
5. After sending notice the following error popup when LogicMail attempts to set the Reply/Forward indicator flag: "Invalid mailbox for message"

This can be easily solved by adding calls to checkActiveFolder() into the IncomingMailConnectionHandler methods for message flag update requests.

[octo]

In [835]:

Added calls to checkActiveFolder() to all flag change methods it was missing from (fixes #299)