Assume UTC if no timzone spec'd in INTERNALDATE: Closes bgo#728647

Netcourrier.com issues INTERNALDATEs with no timezone/UTC offset
specified.
Make Geary compat. with mail.ru and netcourrier.com: Closes bgo#714902

imap.mail.ru and imap.netcourrier.com both do not parse this IMAP
request:

a001 FETCH 1 BODY[HEADER.FIELDS (FIELDS)]

The problem is the space between "HEADER.FIELDS" and "(FIELDS)", which
is valid IMAP.

This patch introduces detection of this problem and falls back to an
IMAP syntax where the space is removed.  Since other servers don't
recognize this syntax, it's important to detect this specific case and
use it.

Since multiple servers have reported this problem, this approach
rather than a list of hacks by domain name was adopted.  If this
detection algorithm has unintended side-effects, a domain-name listing
may be considered later.
Fix bug introduced in prior commit

Prior commit would retry FETCH command for *any* Error, which is
incorrect.  It should only retry when RETRY is thrown, otherwise it
should re-throw the Error.
Prevent AccountSynchronizer from deadlock

Occassionally the EmailPrefetcher would not signal its work was
completed, causing the AccountSynchronizer to deadlock (it waits
until the EmailPrefetcher completes before closing the Folder and
moving on to the next one).  The problem was due to the
EmailPrefetcher not clearing a timeout id, making other code think
other work was outstanding when it was in fact completed.
Don't allow copy/move message to save folder: Bug #731879

The Folder implementation returns with no error if attempted and the
folder menu item is disabled in the drop-down copy/move menus.
Prevent losing emails during move operation: Bug #731561

Move operation could lose emails if the copy destination doesn't
exist (or quota reached, etc.)  This de-pipelines the move operation
into a copy and a delete, guaranteeing the delete only occurs if the
copy succeeds.