Change the VTKM_CONT_EXPORT to VTKM_CONT. (Likewise for EXEC and
EXEC_CONT.) Remove the inline from these macros so that they can be
applied to everything, including implementations in a library.
Because inline is not declared in these modifies, you have to add the
keyword to functions and methods where the implementation is not inlined
in the class.
VertexClustering previously only worked with data of a specific floating
point type (32 bit for point coordinates). Add some templates to accept
either 32 bit or 64 bit floating points for point coordintes and be a
bit more careful about implicit type conversions.
I also made some changes to conform better with the VTK-m coding
standards. The most common changes are using 2 space indentation for all
block levels, capitolizing and using camel case for all class members,
and prefixing "this->" to all use of internal class members.
