LayoutLib: Switch SimpleDateFormat to icu.

Use ICU's implementation of SimpleDateFormat in LayoutLib. The format
patterns used are not supported by java.text.SimpleDateFormat.

The change required adding a mechanism for promoting visibility of
fields in the framework in the create tool.
TODO: Add additional tests in the create tool for this new
functionality.

Change-Id: Id0f4be41f9731c42a28919c32cc5ef271a656982