COMP: C++11 conformance for static initialization

error: non-constant-expression cannot be narrowed from type 'unsigned long' to 'IndexValueType' (aka 'long') in initializer list [-Wc++11-narrowing]
as identifiied by the clang compiler.

From: Hans Johnson <hans-johnson@uiowa.edu>

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22913 3bd1e089-480b-0410-8dfb-8563597acbee
COMP: C++11 compiler warning convert NULL to bool

warning: implicit conversion of NULL constant to 'bool' [-Wnull-conversion]

From: Hans Johnson <hans-johnson@uiowa.edu>

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22914 3bd1e089-480b-0410-8dfb-8563597acbee
COMP: C++11 convertsion of types

error: no viable conversion from 'DiffusionTensor3DExtended<float>' to 'DiffusionTensor3DExtended<double>'

By preferring initialization to assignment this error is avoided.

From: Hans Johnson <hans-johnson@uiowa.edu>

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22915 3bd1e089-480b-0410-8dfb-8563597acbee
BUG: Fixed various errors in the save scene dialog for mrb format

There were 3 problems:
1. When the save scene dialog is shown first, the file format selector is empty
2. When a scene is saved as .mrb and then the save dialog is opened again the format is still .mrb, but the populated items are not disabled
3. When a scene is saved as .mrb and then the save dialog is opened again the target directory is not the same (it’s the parent directory of the directory where the scene was saved the last time)

From: Andras Lasso <lasso@queensu.ca>

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22916 3bd1e089-480b-0410-8dfb-8563597acbee