Fix bug #1217096
newdb: Fix timezone problem in custom column date edit widgets

Fix a regression that could cause the dates in custom date-type columns
to change in some timezones when using th edit metadata dialog to make
unrelated changes. Fixes #1217096 [After updating metadata (i.e. new cover) home made date column (YYYY) is adjusted too](https://bugs.launchpad.net/calibre/+bug/1217096)

Merge branch 'master' of https://github.com/cbhaley/calibre
Move delete to recycle bin into a separate process on windows

This will hopefully fix any remaining locking errors on windows.