Force a metadata backup when adding, deleting, or changing the structure/metadata of a custom column.
Bah. Forgot to select all the changed files.
Trigger backup for all books when adding/modifying a custom column

Merge branch 'master' of https://github.com/cbhaley/calibre
Update last_mod times when custom column metadata changes instead of triggering a backup.
Avoid re-writing all OPF files on custom column metadata change

Merge branch 'master' of https://github.com/cbhaley/calibre
...
Phys Org by Krittika Goyal
PDF Output: Serialize ToC string as UTF-16

PDF Output: Fix non-breaking space characters incorrectly rendered in
PDF outline. Fixes #1223862 [PDF TOC -  &nbsp; appears sometimes as €](https://bugs.launchpad.net/calibre/+bug/1223862)
Driver for PocketBook Mini 515

Fixes #1223853 [Pocketbook 515 recognition](https://bugs.launchpad.net/calibre/+bug/1223853)
Book polishing: Apply null comments

Book polishing: Do not leave behind the old comments when updating
metadata if the comments have been deleted in calibre.
Driver for "OPPO Find 5" Android phone
Merge pull request #79 from Cykooz/oppo_phone

Driver for "OPPO Find 5" Android phone
Better name for immediate_backup
Remove non-existent columns from the set of columns to display. Having them there can cause exceptions.
Merge branch 'master' of https://github.com/cbhaley/calibre
Update Harvard Business Review
Caravan Magazine by Kovid Goyal
ODT Input: Only use the first image as cover

ODT Input: Only treat the first image as a cover if it is of suitable
size, instead of any image in the document. See #1224157 (ODT to MOBI - Images - Cover Image will not removed and other images are missed)
pep8
version 1.3