* Add url/voice options to audio sources
* Add help for TTS
* Remove old settings
* Update tests
* Update use of audio source URL
* Improve labels for sources with the same type
* Update dictionary settings structure to use an array instead of an object
* Update ensureDictionarySettings implementation
* Remove some usage of ObjectPropertyAccessor
* Add double-down-chevron.svg
* Add options
* Update dictionary importers
* Update settings
* Add support for collapsible definitions
* Improve case when there is a very small amount of overflow
* Fix incorrect enabled state of newly imported dictionaries