Extend test generator to generate tests for Float16

http://b/27512382

Extend the test generator to add a short and double field to the
Arguments class for Float16 parameters.  Input short values get
converted to double while initializating the Arguments class and output
short values get converted to double before invoking
Target.Floaty.couldBe().

Change-Id: I9848cb4b2ba7b79c5b77d849a4c48e827d24f64c
3 files changed