GitLab

  - replaces floating-point equal comparisons in
    `linearEqn`, `quadraticEqn`, and `cubicEqn`,
  - ensures `quadraticEqn` and `cubicEqn` can return `complex` roots,
  - reorders if-branches in `quadraticEqn` and `cubicEqn` to avoid
    zero-equal comparison,
  - adds Kahan's cancellation-avoiding algorithm into `quadraticEqn` and
    `cubicEqn` for the numerically-sensitive discriminant computation,

  - adds/improves `polynomialEqns` tests:
    * adds Test-linearEqn.C
    * adds Test-quadraticEqn.C
    * improves Test-cubicEqn.C

Applied to eigen-value calculations. Fixed repeated-eigen-value issues
in eigen-vector generation.

- Rewrote globalPoints to use globalIndex class so now only transfers
single label instead of labelPair
- Added addressing in globalMeshData
    - from coupled master points to slave points
    -         ,,          edges     ,,    edges
    - from coupled points (master or slave) to uncoupled boundary faces
    -               ,,                    ,,                      cells
- See test/globalMeshData for simple test