Fix Loki initialisation in Extrapolate for threading.

This MR fixes a bug in Extrapolate class with Loki initialisation.

See merge request !492

Fix/doc

This MR fixes a number of content and formatting issues with the user guide and developers guide. It adds some missing options and features in the earlier section of the user guide. The formatting and quality of the HTML output is improved with a number of fixes for tables, note/tip boxes and the CSS, although still not perfect.

See merge request !485

Fix/zlib install mac

This MR fixes install paths for OS X when compiling zlib from third party sources. It also removes now unneeded linker flags since CMake handles library dependencies properly.

See merge request !484

Fix some warnings on OS X

Fixes a few compiler warnings on OS X and makes string comparisons against session file parameters case-insensitive in `ForcingMovingBody.cpp`.

See merge request !491

Feature/visit

This MR adds a number of updates and fixes to support the VisIt visualization package reading Nektar++ fld files. Specifically, this fixes a virtual function bug and adds the list of XML input files to the metadata of field files.

See merge request !490

Feature/compressible bl

This branch introduces two new utilities in the CFS folder for generating compressible BL on a 2D/3D flat-plate.

See merge request !439

Add adiabatic wall boundary conditions to CFS

This MR adds support for adiabatic wall boundary conditions to the compressible flow solver.

See merge request !430

Fix/iterative static cond

See merge request !483

Fix/update version 4.1.0

Update to version 4.1.0

See merge request !482