[Evolution] EWS users: remove your cache

[David Woodhouse <dwmw2 infradead org>]

When updating to today's Evolution-EWS snapshot, you should:
 - Disable your EWS account
 - Quit Evolution
 - rm -rf ~/.local/share/evolution/mail/ews/
 - Restart Evolution
 - Re-enable your EWS account

This will blow away your cache entirely, and disabling/enabling the
account will also cause it to recreate the configuration entries for
your calendar folders.

This should mean that UIDs of calendar items are now preserved correctly
and we no longer have the dirty hack where we override them to be the
Exchange server's ItemId for the object because we can't get the real
UID.

We *can* get the real UID, but in order to do that we have to require
Exchange 2007SP1 and *all* the opaque ItemIds for *all* objects
(folders, messages, calendar items, etc.) suddenly change when you do
that â which is why we have to ditch the cache.

Exchange is *such* a pile of crap... 

Hopefully this should be the last time we have to do this.

-- 
dwmw2