utf8: implement utf8foldernames option

If utf8foldernames is enabled on account level all folder names read
from the IMAP server will immediately be reencoded to UTF-8. Names
will be treated as UTF-8 as long as the IMAP server isn't contacted again,
for which they are reencoded to IMAP4-UTF-7.

This means that any further processing such as nametrans, folderfilter
etc. will act upon the UTF-8 names, which will have to be documented
carefully.

NOTE 1:
GMail repositories and folders inherit from the IMAP... classes, so I don't
know yet if these changes have ugly side-effects. But web research suggests
that GMail IMAP folders are equally encoded in UTF-7 so that should work
identically here and incorporate the same improvements.

NOTE 2:
I could not test the behaviour with idlefolders as I didn't get this option
to work at all, not even with the latest stable version.

NOTE 3:
I *did* test to sync an IMAP repository against another IMAP repository.

Signed-off-by: Urs Liska <git@ursliska.de>
Signed-off-by: Nicolas Sebrecht <nicolas.s-dev@laposte.net>

offlineimap/accounts.py

@@ -69,6 +69,8 @@ class Account(CustomConfig.ConfigHelperMixin):
         self.name = name
         self.metadatadir = config.getmetadatadir()
         self.localeval = config.getlocaleval()
+        # Store utf-8 support as a property of Account object
+        self.utf_8_support = self.getconfboolean('utf8foldernames', False)
         # Current :mod:`offlineimap.ui`, can be used for logging:
         self.ui = getglobalui()
         self.refreshperiod = self.getconffloat('autorefresh', 0.0)
@@ -360,7 +362,7 @@ class SyncableAccount(Account):
 
                 if not remotefolder.sync_this:
                     self.ui.debug('', "Not syncing filtered folder '%s'"
-                                  "[%s]"% (remotefolder, remoterepos))
+                                  "[%s]"% (remotefolder.getname(), remoterepos))
                     continue # Ignore filtered folder.
 
                 # The remote folder names must not have the local sep char in
@@ -378,7 +380,7 @@ class SyncableAccount(Account):
                 localfolder = self.get_local_folder(remotefolder)
                 if not localfolder.sync_this:
                     self.ui.debug('', "Not syncing filtered folder '%s'"
-                                 "[%s]"% (localfolder, localfolder.repository))
+                                 "[%s]"% (localfolder.getname(), localfolder.repository))
                     continue # Ignore filtered folder.
 
                 if not globals.options.singlethreading: