Fix issues caught by Android Lint

Fixes:
external/androidplot/Examples/DemoApp/res/values/style.xml:17: Warning: Unexpected namespace URI bound to the "android" prefix, was http://schemas.android.com/apk/lib/com.androidplot.xy, expected http://schemas.android.com/apk/res/android [NamespaceTypo]

Test: rerun lint
Change-Id: I74b535b92c4aa81b4d60ec7504ebd1cce51234a7