- remove all sembast code
- setup database migration system
- setup data import export system
- remove sembast object tests
- make everything ready for implementing "saved lists" feature
* Add lots of new functionality to search results
* Fix jlpt level
* Make antonyms clickable
* Add kanji list
* Replace Blocof with BlocBuilder
* Make kanji widgets squared
* Add missing colons to headers
* add romaji under sentences
* Fix extensive search not showing
* Miscellaneous refactoring