Argument and index symmetries of Passarino-Veltman functions

[vsht]

Dear FeynCalc users,

it has been observed multiple times (e.g. here but also via private
communication) that FeynCalc doesn't implement symmetries between
Passarino-Veltman functions with different indices and argument orderings,
apart from C0 and D0.

It has been on my ToDo list for quite some time and finally I found
a convenient way to tabulate such relations (using FeynCalc, of course)
in a manner that can be directly extended to more legs and higher ranks.

With the recent commit to the dev version, all PaVe functions should now
automatically order their arguments in a "canonical" way. However,
in general, to minimize the number of PaVes in an amplitude this may not
be sufficient. Therefore, I also updated the documentation page on PaVeOrder
to show how one can approach this task by testing different argument orderings:

https://github.com/FeynCalc/feyncalc/blob/master/FeynCalc/DocumentationFiles/Markdown/PaVeOrder.md

Hope this helps and looking forward to some feedback on the new PaVeOrder.

Cheers,
Vladyslav