Add Ktlint and editorconfig file

[elcolto]

Integrate Ktlint to ensure continuous and defined formatting on all Kotlin files. So IDE updates and local settings wouldn't effect existing code. Ktlint is configured by added .editorconfig file. Kept as slim as possible. Stick to "old" intellij_idea code style, which causes the less changes in formatting. ktlint_official would cause many formatting violations.