Add own dependency on Logback because ProB 2 no longer provides it

build.gradle

@@ -37,6 +37,7 @@ configurations.all {
 }
 
 dependencies {
+	implementation(group: "ch.qos.logback", name: "logback-classic", version: "1.2.3")
 	implementation(group: "com.google.code.gson", name: "gson", version: "2.8.6")
 	implementation(group: "com.google.guava", name: "guava", version: "28.2-jre")
 	implementation(group: "de.hhu.stups", name: "de.prob2.kernel", version: "4.0.0-SNAPSHOT")