Split graph_generators into several files

[ncohen]

This tickets addresses the fact that Jeroen is not happy with the length of graph_generators.py :-P

It splits the file into new ones, added in the graph/generators/ folder, according to the classifiation of the methods that appears in the module's documentation.

APPLY:

• trac_13862.patch​
• trac_13862-cleaning_and_moving.patch​
• trac_13862-doc.patch​

[ncohen]

This patch creates the following files and moves into them the methods from GraphGenerator that are associated to it in the list at the top of the graph_generators module documentation.

• basic.py
• degree_sequence.py
• families.py
• platonic_solids.py
• random.py
• smallgraphs.py
• world_map.py

This patch passes all tests, but is not clean yet and lacks documentations. Others will follow.

Nathann

[ncohen]

What this additional (trac_13862-cleaning_and_moving.patch​) patch does :

• Moves _circle_embedding and _line_embedding to graph_plot.py. These methods are now imported at the beginning of generators/* modules that need need.
• Removes LCFGraph from the list of basc graphs (this methods creates a family of graphs). It was already in the list of "families" graphs.
• Moves the Harary Graph to the "families" file. Same thing here : there are many Harary graphs.
• Moves DorogovtsevGoltsevMendesGraph to families.py. Not worth creating an independent "pseudofractal" module at the moment.
• Moves IntervalGraph to families. This one was not liste among the "families", which is why it was still in graph_generators.py after the first patch.
• Adds the Nauru Graph to the list of small graphs.

Some work on the doc is still needed.

Nathann

[ncohen]

Apply trac_13862.patch, trac_13862-cleaning_and_moving.patch

[ncohen]

What this new patch (trac_13862-doc.patch​) does :

• Moves the "Usage" part of the graph_generators module's doc to graph_plot, as it explains how graphs are displayed.
• *HEAVY* rewrite of the fuctions lists at the top of graph_generators. Now the methods are listed in 3xN tables, so that they are easier to browse. This required to define an (ugly) helper function in graph_generators.py. But the lists at the top of that file are now easier to read (both in html and in sage.graphs.graph_generators?) and easier to update (just add a string in a list).
• NauruGraph isadded to the list of small graphs

This patch's almost ready.

Nathann