chore(gradle): add root settings for uatu multi-project build

Links :sidecar and :sdk-android under one wrapper. Root build.gradle
provides a clean task that wipes the root build dir.

gradle.properties

@@ -0,0 +1,5 @@
+org.gradle.jvmargs=-Xmx2048m -Dfile.encoding=UTF-8
+org.gradle.parallel=true
+org.gradle.caching=true
+kotlin.code.style=official
+android.useAndroidX=true