Adding recipes for building deal models

[yellowbean]

it's not easy to build with feeding all python list/maps into Generic class.

• How about pre-include template deals in the library, then user can pull one of them and tweak the structure ?

make_gnma_deal(....)

• Or , build a smart deal factory, user feeds it with a chain of instructions to describe how deal looks like, then the factory function will build the deal instead.

build_deal(OC=115%,bond=(), waterfall=(....).......