Generate an abbreviation F X for F.axioms X (fix #61)

[gares]

Two things to do:

• demo2 has an error since TAddAG is also a definition (before it becomes a structure). @CohenCyril I let you decide what to do
• We need to replace all F.axioms by F in the files

Question:

• now Foo is the type of the factory, while Foo.Axioms is the constructor. Maybe we should rename/alias it to something nicer? Foo.Build maybe? The last commit implements it, it is easy to drop

[CohenCyril]

• demo2 has an error since TAddAG is also a definition (before it becomes a structure). @CohenCyril I let you decide what to do

The typealias TAddAG should be renamed tAddAG

[gares]

Well, I've added a trailing _, feel free to push here

[CohenCyril]

LGTM