[Structure] Refactor App class to Kotlin. Rewrite SzkolnyTask and posting notifications. Remove dependency on AppConfig. Update libraries and gradle.

nachos/build.gradle

@@ -1,11 +1,11 @@
 apply plugin: 'com.android.library'
 
 android {
-    compileSdkVersion 28
+    compileSdkVersion setup.compileSdk
 
     defaultConfig {
         minSdkVersion 15
-        targetSdkVersion 28
+        targetSdkVersion setup.targetSdk
         versionCode 1
         versionName "1.0"
     }