feature/mesh-spacing

The applies changes ask for my spencer after the madrid tutorial, BL resolution and variable names etc.
It also fixes the inverted boundary layer problem.
Finally, allows the variational module to be compiled without meshgen.

See merge request !736

Fix half mode in FieldConvert

This fixes a small bug which prevents FieldConvert from working with half mode expansions.

See merge request !734

Fix/iterative rhs magnitude

This MR fixes a bug in the calculation of the RHS vector magnitude used to scale the tolerance calculation, which resulted in an artificially higher tolerance being used.

Also fixes a bug in the verbose iteration count output of the CG algorithm when no iterations are performed.

See merge request !721

Conflicts:
	CHANGELOG.md

added documentation for the chk file backup

See merge request !727

Add hybrid performance model.

This MR adds a performance model for hybrid 2.5D simulations using the incompressible Navier-Stokes solver.

See merge request !724

Small CMake modification to MacPorts and Homebrew detection to fix OCE

This MR fixes Homebrew and MacPorts detection in OCE by unsetting appropriate variables if the installation has not been found. Consequently, OCE detection now works properly for Homebrew.

See merge request !729

fix/surface-mesher

Fix bug in compilation, tests and surface mesher.

See merge request !728