ThOr functor references update

To be tested with Rec!3307 (merged)

Update of the script that automatically generates the ThOr functors reference page for the documentation. It helps to address (part of) Rec#435 (closed).

To be coherent and have nice references, all the "basic functors" or "vocabulary functors" have the correspondent C++ string representation followind their description, representing the namespace and the name of the struct where the functor is defined. "Composed functors" have instead a description of the composition structure that characterize them. Only composed functors which have explicit arguments have a proper link to their implementation.

Follows Rec!3241 (merged)

• Add test while building the ThOr-LoKi translation table about the rows' length (see discussion !1993 (comment 6332702))
• Fix translation table for entries with more than 4 columns
• Add require_any to HELPERS, SSPionBDT* to functor's references
• Remove the obsolete "_headers" attribute check in make_functor_docs.py
• Add "_template_parameters" attribute to the list of parameters (related to #366)
• Report python composition for composed functor and C++ string representation (with namespace) for basic functors

TODO:

• test doc final result