Use SHA256 of EWS ItemId for cache filename, not the ItemId itself.
Use SHA256 of EWS ItemId for cache filename, not the ItemId itself.

An ecryptfs user complained; it can't handle long filenames.

Use the sha256 of the id instead, and automatically rename old files as we
try to open them.

GNOME/evolution-ews,GNOME/evolution-ews