Convert uhabits-server/build.gradle to Kotlin; use standard paths

uhabits-server/src/main/resources/application.conf

@@ -0,0 +1,9 @@
+ktor {
+    deployment {
+        port = 8080
+        port = ${?PORT}
+    }
+    application {
+        modules = [ org.isoron.uhabits.sync.app.SyncApplicationKt.main ]
+    }
+}