refs #8034. Directly to Stitch1D algorithm.

Simply wire-in the Stitch1D algorithm. Get rid of the existing messy implementations. We now get System test coverage for Stitch1D, and conversely get Unit test coverage for aspects of combineMulti via Stitch1D.
refs #8034. More removal of code.

Take out unnecessary block of code and imports. Everything still works fine.
Merge remote-tracking branch 'origin/feature/8034_combinemulti_stitch1d'