Merging branch 'j.0'  into 'main'.

See merge request !2765

Merging branch 'm.1'  into 'main'.

See merge request !2764

[a.newInstallMethod] Add a new installation method for local installation under Linux (Closes #1023, #950, #949, and #938)

Merging branch 'a.newInstallMethod'  into 'main'.

A new installation method is implemented for local installation under Linux.
This is performed by the command `make install_local` or `ninja install_local` (as opposed to the default `make install` or `ninja install`)
and installs the BornAgain executable and BornAgain libraries to the system folders.

This was a request by Georg Brandl (31 Jan 2024).

To set the directories, `GNUInstallDirs` is used as the standard (issue #949).

Minor improvements made to the CMake scripts.

See merge request !2760

Closes issue #949

Merging branch 'm.0'  into 'main'.

See merge request !2763

Merging branch 'm.0'  into 'main'.

See merge request !2762

Merging branch 'm.0'  into 'main'.

See merge request !2761