BUG #14813: Fix range reported for mode shapes.

Since mode shapes in Exodus are index starting with 1, we add a new API
to vtkExodusIIReader to report this range explicitly, rather that users
having to deduce the range from TimeStepRange.

Change-Id: I761ee20590cf1c0cbdfa152b77534dc508a60676
Merge topic '14813_fix_mode_shapes_range' into master

2327e0ac BUG #14813: Fix range reported for mode shapes.