Refactor HTML syntax highlighter too keep track of tag nesting

This is needed for the eventual implementation of inline spellcheck
Start work on managing dictionaries in calibre
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Add ISO 3166 country codes
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Implement loading of both builtin and user installed dictionaries
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Start work on dialog to manage user installed dictionaries
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Start work on adding dictionaries
Add/remove for dictionaries from OpenOffice extensions  works
Implement renaming of dictionaries
Integrate the dictionary widget into the editor preferences
Keep track of the current book's locale as a separate global variable for performance
Refresh all editors after changing dictionaries
Add Spanish and English (GB) builtin dictionaries
Add code to get all words from a ebook with their declared locale
Try to use the right country variant english dictionary by default, based on the users locale settings
Ignore title/alt attributes on some tags
Start work on spell check dialog