samples: Add an aggregate task for samples

samples/build.gradle

@@ -28,4 +28,12 @@ task buildSamplesWithPlatformLibs() {
     dependsOn ':uikit:build'
     dependsOn ':win32:build'
     dependsOn ':workers:build'
+    dependsOn ':calculator:build'
+
+}
+
+task buildAllSamples() {
+    subprojects.each {
+        dependsOn(":${it.name}:build")
+    }
 }

samples/settings.gradle

@@ -1,3 +1,5 @@
+// NOTE: If a new sample uses only platform libs,
+// please add it into the 'buildSamplesWithPlatfromLibs' task in build.gradle.
 include ':calculator'
 include ':csvparser'
 include ':gitchurn'
@@ -5,7 +7,6 @@ include ':gtk'
 include ':libcurl'
 include ':nonBlockingEchoServer'
 include ':opengl'
-include ':python_extension'
 include ':socket'
 include ':tetris'
 include ':tensorflow'