demos: Give Android versions permissions for internet & read/write files

demos: Give Android versions permissions for internet & read/write files

This is in support of RenderDoc (and other tracing libraries).  On Android,
these "native" applications must have permission to read/write files on the
Android filesystem so that a trace-capture library can write a trace file.
After building and installing the application, the following commands should be
run from a Linux shell, in order to truly grant those permissions (not normally
required for an Android Java-based app, with a GUI; but is required for these
shell-launched, native apps):

adb shell pm grant com.example.Cube android.permission.READ_EXTERNAL_STORAGE
adb shell pm grant com.example.Cube android.permission.WRITE_EXTERNAL_STORAGE