Document that '%' needs encoding as '%%' in offlineimap.conf

We use python's SafeConfigParser, and this is a built in "feature" used
for interpolating variables. But it imples that '%' needs encoding as
'%%'.

Signed-off-by: Sebastian Spaeth <Sebastian@SSpaeth.de>

Changelog.rst

@@ -11,6 +11,7 @@ WIP (add new stuff for the next release)
 * bump bundled imaplib2 library 2.29 --> 2.33
 * Actually perform the SSL fingerprint check (reported by J. Cook)
 * Curses UI, don't use colors after we shut down curses already (C.Höger)
+* Document that '%' needs encoding as '%%' in *.conf
 
 OfflineIMAP v6.5.3.1 (2012-04-03)
 =================================

offlineimap.conf

@@ -21,6 +21,7 @@
 #
 # would set the trashfolder setting for your German gmail accounts.
 
+# NOTE2: This implies that any '%' needs to be encoded as '%%'
 
 ##################################################
 # General definitions
@@ -341,7 +342,7 @@ remoteuser = username
 #    OfflineIMAP starts when using a UI that supports this.
 #
 # 2. The remote password stored in this file with the remotepass
-#    option. Example:
+#    option. Any '%' needs to be encoded as '%%'. Example:
 #    remotepass = mypassword
 #
 # 3. The remote password stored as a single line in an external