fix issue #110 kotlin-dsl

[shikajiro]

Issue

• close #110

Overview (Required)

• build.gradle files change to build.gradle.kts
• create buildSrc dir. Versions.kt file is management library versions. ex:

  
  object Versions{
  const val compileSdk = 27
  }

android{ compileSdkVersion(Versions.compileSdk) }

I made a kotlin file without using `ext`.
Because code completion can be used.

- Depends.kt file is management dependencies libraries.

ex:

object Depends { object Kotlin { val stdlib = "org.jetbrains.kotlin:kotlin-stdlib-jre7:${Versions.kotlin}" ...

implementation(Depends.Kotlin.stdlib)

- settings.gradle can not change to kts. It causes some compile error 😣

- I checked build & run. But I can not check deploy to Google Play.

## Links
- https://github.com/gradle/kotlin-dsl
### respect
- https://qiita.com/chibatching/items/d63c0c9afc8e1e6bc9de
- https://qiita.com/chibatching/items/3b40aea222b2a2f29d4b
- https://github.com/chibatching/KtsSample
- https://github.com/jaredsburrows/android-gif-example
- https://github.com/justjanne/QuasselDroid-ng

## Screenshot
no file

[takahirom]

🆒

[takahirom]

LGTM 👍 I want to try that 😄