* Refactor _groupTerms and add doc comment
* Update where expression/reading is acquired from
* Add doc comment
* Add isPrimary field
* Update test data
* Add definition which has "isPrimary": false definitions
* Update implementation of _buildTermMeta
* Remove old implementation
* Expose dictionaryPriority on frequencies and pitch accents
* Update how meta data is generated; add index
* Update order
* Update names
* Expose expressionIndex as part of pitch/frequency data
* Implement meta sorting
* Update test data
* Move bg/js/anki.js to js/comm/anki.js
* Move bg/js/mecab.js to js/comm/mecab.js
* Move bg/js/search-main.js to js/display/search-main.js
* Move bg/js/template-patcher.js to js/templates/template-patcher.js
* Move bg/js/template-renderer-frame-api.js to js/templates/template-renderer-frame-api.js
* Move bg/js/template-renderer-frame-main.js to js/templates/template-renderer-frame-main.js
* Move bg/js/template-renderer-proxy.js to js/templates/template-renderer-proxy.js
* Move bg/js/template-renderer.js to js/templates/template-renderer.js
* Move bg/js/media-utility.js to js/media/media-utility.js
* Move bg/js/native-simple-dom-parser.js to js/dom/native-simple-dom-parser.js
* Move bg/js/simple-dom-parser.js to js/dom/simple-dom-parser.js
* Move bg/js/audio-downloader.js to js/media/audio-downloader.js
* Move bg/js/deinflector.js to js/language/deinflector.js
* Move bg/js/backend.js to js/background/backend.js
* Move bg/js/translator.js to js/language/translator.js
* Move bg/js/search-display-controller.js to js/display/search-display-controller.js
* Move bg/js/request-builder.js to js/background/request-builder.js
* Move bg/js/text-source-map.js to js/general/text-source-map.js
* Move bg/js/clipboard-reader.js to js/comm/clipboard-reader.js
* Move bg/js/clipboard-monitor.js to js/comm/clipboard-monitor.js
* Move bg/js/query-parser.js to js/display/query-parser.js
* Move bg/js/profile-conditions.js to js/background/profile-conditions.js
* Move bg/js/dictionary-database.js to js/language/dictionary-database.js
* Move bg/js/dictionary-importer.js to js/language/dictionary-importer.js
* Move bg/js/anki-note-builder.js to js/data/anki-note-builder.js
* Move bg/js/anki-note-data.js to js/data/anki-note-data.js
* Move bg/js/database.js to js/data/database.js
* Move bg/js/json-schema.js to js/data/json-schema.js
* Move bg/js/options.js to js/data/options-util.js
* Move bg/js/background-main.js to js/background/background-main.js
* Move bg/js/permissions-util.js to js/data/permissions-util.js
* Move bg/js/context-main.js to js/pages/action-popup-main.js
* Move bg/js/generic-page-main.js to js/pages/generic-page-main.js
* Move bg/js/info-main.js to js/pages/info-main.js
* Move bg/js/permissions-main.js to js/pages/permissions-main.js
* Move bg/js/welcome-main.js to js/pages/welcome-main.js
