Add em tags around button title

to distinguish the button title better from the rest of the text, there should be something around it like <em> tags.
Merge branch 'patch-1' of https://github.com/nerdoc/calibre
Edit Book: When using the spell check dialog to change words, detect any changes made to open files outside the spell check dialog and automatically integrate them, to prevent those changes from being lost.
Edit book: Spell checker: Treat hyphenated words as single words for spell checking
pep8
When clicking in the search box, select all existing text, for easy replacement. Fixes #1338862 [[Enhancement] Search enhancements](https://bugs.launchpad.net/calibre/+bug/1338862)
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
note about creating import checker