Making VisIt bridge compatible with the way readers are loaded.

ParaView was changed so that the definition of the readers
(including their extensions) was obtained solely from the server
instead of using a special file to associate a reader with
a file extension on the client. That extension association was
already in most of the XML descriptions in the hints for readers
anyways. So now as long as a reader is built on the server
it will be available on the client, independent of whether the
client was "built" with that reader. These changes to the VisIt
bridge take advantage of those changes.
Updated the dependencies for private dependencies

vtkIOImage was only there for vtktiff, added in the correct dependency
and removed what looks like a defunct variable (VTK_TIFF_LIBRARIES).
Avoid bringing int64_t into the global namespace

This causes issues with newer C99 conformant compilers where it is
already there, instead refer to the type in the boost namespace.
Fixed module dependencies.

Fixes module dependencies after public/private depdencies in VTK modules were
updated.
Update visit to use link_public and link_private.
Merge branch 'private_deps'