caused by faMesh::faceAreaNormals() in a loop. Removed from the loop but the underlying finiteArea code (class faMesh) may need more attention.

Integration 1712

See merge request !1

- combine library sources into a single faAvalanche library

- solvers and utilities under applications/

- tutorials run/clean using standard functions

- in many places just have a dimensioned Zero value, which can be
  written compactly.
  Eg,
      dimensionedScalar(dimVelocity) is the same as
      dimensionedScalar("0", dimVelocity, Zero)