Edit Book: Allow putting the editor into replace mode by pressing the Insert key
Edit Book: When refreshing the ToC view pick up the unsaved changes, if any, in the ncx file
Edit Book: Update the Table of Contents view automatically when the ncx file is edited.

Also avoid unnecessary rebuilds of the Table of Contents view.
Ignore errors during live refresh of the toc view
E-book viewer: When using the tap and hold gesture on a touchscreen, allow lookup  of the word currently under the finger in the dictionary or online. Fixes #1318242 [Enhancement: allow text select on Windows Tablet, perhaps with stylus](https://bugs.launchpad.net/calibre/+bug/1318242)
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Make word under cursor detection more robust
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
Get rid of the PyQt4 string from everywhere
Port: setMargin() reset() QStringList()

setMargin(): QLayout no longer has a setMargin() function, replace with
setContentsMargins()

reset(): QAbstractListModel no longer has reset(), replace with
beginResetModel(), endResetModel()

QStringList: No longer exists, a simply python list of strings works
instead
Fix mouse wheel not working in diff view
Port coffeescript compiler
Add note about headless Qt QPA plugin
Port WebKit imports and QChar

WebKit has been split up into QtWebKit and QtWebKitWidgets. Change
imports accordingly.

Replace use of QChar since it no longer exists in PyQt5
Port syntax highlighters