BUG: fix typo in AdditionalInitializeStep method name

Fixing a mis spelling in the additional initialize step method name.
In vtkMRMLAbstractDisplayableManager it's defined as:
AdditionalInitializeStep
but vtkMRMLCameraDisplayableManager was using:
AdditionnalInitializeStep
with an extra n. Using that signature, it was never getting called
so when new layout windows were being created, the active camera
was not getting set on the renderer.

Issue #1690



git-svn-id: http://svn.slicer.org/Slicer4/trunk@22611 3bd1e089-480b-0410-8dfb-8563597acbee
BUG: refactor code to remove unnecessary error message

There are two possible ways to obtain the results from PETStandardUptakeValueComputation,
having them written out to a .csv file or to a string parameter file that gets
parsed and loaded into the Slicer GUI. Only print out an error and fail if
neither parameter is specified. 
Checks for empty strings and doesn't try to open the files, so the unable
to open error messages will only occur if a non empty file name fails
to open.

Issue #3432


git-svn-id: http://svn.slicer.org/Slicer4/trunk@22612 3bd1e089-480b-0410-8dfb-8563597acbee