AI 147162: Emphasize in the javadoc that the "pkg" parameters to

AI 147162: Emphasize in the javadoc that the "pkg" parameters to
  InstrumentationTestCase and its descendants should be the
  package manager package name (not the java package name, and
  not the test package) of the package holding the Activity
  under test.
  Added similar notations to the ApiDemos call sites.
  JAVADOC ONLY - should be safe change for cupcake sdk.
  BUG=1783981

Automated import of CL 147162