Virtual libraries as tabs above book list

Add an option to display virtual libraries as tabs above the book list.
Convenient to quickly switch between virtual libraries. To enable, click
the Virtual library button and select 'Show virtual libraries as tabs'.
You can re-arrange the tabs by drag and drop and close tabs you do not
want. Right click on the tabs to restore closed tabs.
Email to selected in top level menu

Also show error message when no recipients are selected instead of
silently doing nothing.
Fix adding VL not updating VL tabs correctly
Linux mtp: Update MTP device ids from upstram

Also add id for MT65xx Android Phone. Fixes #1212458 [device not detected by calibre](https://bugs.launchpad.net/calibre/+bug/1212458)
Move non upstream change out of upstream file
Allow customization of comic metadata reader plugin

Allow customizing the comic metadata reader plugin via
Preferences->Plugins to read the series index from either the volume
or the issue number of the comic. Fixes #1211433 [comicinfo metada uses volume instead of issue](https://bugs.launchpad.net/calibre/+bug/1211433)
Add QtXmlPatterns to the linux build as some distros seem to require it
Driver for Samsung Galaxy Young S5360

Fixes #1212918 [Calibre wont recognize Samsung Galaxy young](https://bugs.launchpad.net/calibre/+bug/1212918)
version 0.9.44
...
Fix #1212943 [Minor typo in Calibre message (enble)](https://bugs.launchpad.net/calibre/+bug/1212943)
Mark all books as dirty when deleting custom column
Mark books as dirty only after custom column is actually deleted
...
Start work on DOCX output
Make the backup status dialog a bit bigger
Merge branch 'master' of https://github.com/kovidgoyal/calibre