Output sync timing

Modify the UI:acct and acctdone functions to keep tab of the time
inbetween. Put self.ui.acct() and acctdone() at the right places in
accounts.py so that the timing happens at the right places.

While modifying that loop, flatten the nested try: try: except: finally:
constructs, we require python 2.5 now which copes with that.

At the end of each account sync you will now see something like:
*** Finished account 'test' in 0:05

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

Changelog.draft.rst

@@ -18,6 +18,8 @@ Changes
 
 * Indicate progress when copying many messages (slightly change log format)
 
+* Output how long an account sync took (min:sec).
+
 Bug Fixes
 ---------