DOCX Input: Specify zero default margins for headings

DOCX Input: Fix extra top/bottom margins around headings when the
heading style in word does not specify any top/bottom margins.
DOCX Input: Line breaks at the end of a paragraph

DOCX Input: Fix a single line break at the end of a paragraph not being
rendered as a blank line.
Nicer fix for trailing <br>

Also handles headings and list items with trailing <br>s
Show timestamps in local timezone in viewer metadata page
DOCX Input: Fix various issues with numbering->lists

DOCX Input: Handle numbered paragraphs where the numbering is specified
in the paragraph style, instead of on the paragraph directly. Also
support the use of arbitrary, styled text for bullets.
Increase default max cover size tweak
Update Daily Express
Preserve current book when doing searches

When doing searches or switching between virtual libraries in the main
book list, preserve the current book. The currently selected book will
remain visible if it is present in the results of the search or the
selected virtual library. Fixes #1216713 [After selecting books which belongs to same serie, when returning to main window, we are at the top of the list and not at previously selected item](https://bugs.launchpad.net/calibre/+bug/1216713)
Force a metadata backup when adding, deleting, or changing the structure/metadata of a custom column.
Update Dilema Veche
Bah. Forgot to select all the changed files.
Update Jakarta Post and Jakarta Globe
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.