Reorganize one-row code documentation

[ComboProblem]

I think the one row documentation (cutgeneratingfunctionology/doc/html/igp.html) could benefit from additional organization.

I propose splitting this into several sections:

• Documentation of Examples of Extreme Functions
• Code for minimality tests
• Code for extermality tests
• Code to construct and manipulate functions with fixed values (thing like building a function, using symmetric_2_slope_fill_in, ect)
• Code to construct and manipulate parametric families of functions/constructing parametric elements/ect
• Auxiliary code (every thing else)

This additional organization reflects the tasks of constructing families of functions and then proving that the family is minimal/extreme.

[mkoeppe]

Part of the problem is that currently everything in a .sage file (instead of .py file) ends up in the same Python module. (The documentation is generated from the contents of the Python module.)

That would be the first thing to fix.

[ComboProblem]

So a solution might be to define new submodules (.py files) for the sage files that need to be imported by grouping them in terms of the documentation goals. For example to improve documentation with respect to writing parametric families:

parametric_families_docs.py imports code related to constructing parametric familes like parametric.sage, parematric_family.py, parametric_cpl.sage, and others (i'm not sure if this is an exhaustive list of everything that is used with respect to parametric families, but for the examples sake).