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
Merge remote-tracking branch 'upstream/master'