Set a default for TEMPLATENAME
Set a default for TEMPLATENAME

Make setting an output name prefix (-o) in
antsMultivariateTemplateConstruction2.sh optional.  This requires a
default value for OUTPUTNAME and TEMPLATENAME.  A default for OUTPUTNAME
already exists; this commit adds a corresponding default for
TEMPLATENAME.

stnava/ANTs,stnava/ANTs,stnava/ANTs,stnava/ANTs,stnava/ANTs,stnava/ANTs,stnava/ANTs