Add GridLayout as a support project library.

The library is distributed as a project containing a single jar and resources
but the jar file is built by the Android build system in order to target the
current API.
The code also relies on the R class being generated, which is currently done
manually. The build system uses an intermediary library to compile the R class
so that it doesn't get packaged in the final jar file (same behavior as
compiling the library project with the SDK).

Change-Id: I36ce97d875f2efbb50cca665e9fd0e668f5ba837
diff --git a/v7/gridlayout/project.properties b/v7/gridlayout/project.properties
new file mode 100644
index 0000000..5ca3505
--- /dev/null
+++ b/v7/gridlayout/project.properties
@@ -0,0 +1,15 @@
+# This file is automatically generated by Android Tools.
+# Do not modify this file -- YOUR CHANGES WILL BE ERASED!
+#
+# This file must be checked in Version Control Systems.
+#
+# To customize properties used by the Ant build system edit
+# "ant.properties", and override values to adapt the script to your
+# project structure.
+#
+# To enable ProGuard to shrink and obfuscate your code, uncomment this (available properties: sdk.dir, user.home):
+#proguard.config=${sdk.dir}/tools/proguard/proguard-android.txt:proguard-project.txt
+
+# Project target.
+target=android-7
+android.library=true