Mjulian/all day event fix

This pull request contains:
- A cherry-pick from an existing branch: Adding a variable dumping to the logging class
- A cherry-pick from an existing branch: A first unworking (but disabled) draft for mapi objects cache
- Some logging cleaning
- Added two logging date functions (used to debug this bug)
- The actual fix

It was mainly originated by a wrong parameter given by the kolab plugin function move_event. (if this quick fix wouldn't work fine, we should take a look into the main calendar class)
Also, setting an all-day event to happen at the 12:00:00 of the given day, fixes some minor issues.