Edit book: Fix regression that caused an error when trying to edit files with no defined syntax, such as plain .txt files. Fixes #1318139 [Editor: Synatax-Highlighter error](https://bugs.launchpad.net/calibre/+bug/1318139)
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First error in first_matching_compare documentation
Merge branch 'master' of https://github.com/cbhaley/calibre
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Edit book: Insert tag button: Allow entering attributes along with the tag name to make it easy to repeatedly insert, for example, <span class="special"></span>.
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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