Reorder imports

Introduce a convention for the import order to make imports easier to comprehend. E.g.:

1. Imports of modules from Tabris.js
3. Imports of third-party modules
2. Imports of own app modules

Imports of each part could be sorted like this (from the general to the specific):

1. Imports of default exports (`import ... from "...";`)
2. Imports of all exports (`import * as ... from "...";`)
3. Imports of single/multiple exports with the curly brace syntax (`import {...[, ...]} from "..."`)