Use conventions instead of cross-project configuration

gradle userguide suggests to avoid allprojects/subprojects and use conventions instead

https://docs.gradle.org/current/userguide/sharing_build_logic_between_subprojects.html#sec:convention_plugins_vs_cross_configuration

buildSrc/src/main/groovy/brouter.application-conventions.gradle

@@ -0,0 +1,8 @@
+plugins {
+    id 'application'
+    id 'brouter.java-conventions'
+}
+
+application {
+    distTar.enabled = false
+}