Refactorings.

[simjanos-dev]

This is just a ticket for myself to keep in mind what do I want to refactor. I won't put no-pull-request on it, but please ask if you would like to do something from the list, because some of them will be large and I want to do myself.

• [ ] Put language pair selection UI into a separate vue component on the add dictionary admin page.
• [ ] Move adding a dictionary table into a separate function in the DictionaryService file. Should also move other repeating parts into their own function if possible.
• [ ] After the previous task, probably api creation UI components can be merged into one.
• [ ] Interactive text search state should be in vuex.
• [ ] Daily achievements database table and model can be deleted, but double check.