Prepare UKF for large data run as part of NAMIC and HD project

In my attempts to run UKF on a very large NAMIC related HD project, I ran across many issues that needed to be fixed.

The most critical issue was that the files written by UKF were not valid VTK files (due to the header line being incorrectly formatted).

The next most critical issues involved performance and memory management.  Many unnecessary memory copies are voided by using judicious use of const references rather than copy constructors.