Fix #1349536 [convert do not preserve spaces in <pre>](https://bugs.launchpad.net/calibre/+bug/1349536)
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E-book Viewer: Use wiktionary.org and wordnik.com as dictionary providers instead of dict.org (which no longer exists).

When looking up words, the word definition is now opened in a separate
browser window.  The language of the dictionary to lookup is
automatically selected based on the language of the current book. Fixes #1349548 [dict.org not available](https://bugs.launchpad.net/calibre/+bug/1349548)
Change fosshub mirror used for uploading.
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DRYer
Edit Book: Allow the import files into book action to be added to the toolbar
Edit Book: Clear the Check Book panel when opening a new book
Edit Book: Live CSS: Improve detection of which tag the cursor is inside when there are multiple tags on the same line. See #1350495 (Private bug)
Implement rendering of cover grid emblems
Add a preference to turn emblems on/off
Options to control the size and placement of the emblems
Edit Book: Allow customizing the templates used when creating new, blank HTML/CSS files via Preferences->Editor settings. Fixes #1348986 [Footnote pop-up - new issue](https://bugs.launchpad.net/calibre/+bug/1348986)
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Port compiling of .ui forms
Port imports
Port build script for building PyQt extensions to PyQt5
Port the progress indicator extension to PyQt5
Allow controlling PyQt5 import path via the env var PYQT5_IMPORT_PATH
faster builds