Color map now 'inferno', as in paper.
Intensity scale reduced from 10^-10..1 to 10^-8..1.

Also, some additions to the index.

image pdf

No longer needed, as this index refers to form factors only

(document analytic formula as newly implemented;
mention old numeric method in History section)

integration

(to avoid confusion when doing full-text search)

"Abs" could also mean absolute value ...

Modern way of finding Python on a system

Switch Travis to the new Docker custom ubuntu-focal container. Goal is to have latest Qt and lates cmake, and decrease "install" time.

Switch to old-style way of returning unique_ptr from a function to please ancient Mac OS El Capitan compiler.

Code beautification

Update swig bindings to version 4.0.1