FuncSpec: extract 'reuseterms' setting from __init__

--HG--
extra : rebase_source : 8bae7151833cce91d27487eb5471b5bf327ce12d
FuncSpec: extract 'auxvars' setting from __init__

--HG--
extra : rebase_source : cc35bda25950995b0cfc4d5a91ec54e175c42c41
extra : histedit_source : d464634167727bd1e4d932cc289b86aa741ee8b0%2Cf988f53b7089ff17be4ec69e607c47a5b5c22335
FuncSpec: remove unused imports
FuncSpec: remove unused local variables
FuncSpec: remove useless condition check
FuncSpec: rename local variable in '__init__' to avoid built-in redefining
FuncSpec: simplify keys validation
FuncSpec: check necessary keys early
FuncSpec: extract 'targetlang' setting from __init__
FuncSpec: extract function for building list of names
FuncSpec: support any iterable for vars/pars/inputs names on input
FuncSpec: remove duplication in names setting
FuncSpec: extract input validation to separate method
FuncSpec: add tests for macros to preserve current behaviour
FuncSpec: extract code generation to separate classes
FuncSpec: move code generators to separate modules
codegenerators: add base class and factory method
codegenerators: 'generate_aux' returns built dictionary
codegenerators: shorten names, adjust base class

--HG--
extra : histedit_source : c4c7476d708eb953762c61e41899d29a997aef6c
python: extract generating of buit-in aux functions

--HG--
extra : histedit_source : 6f83779d33ec4ca718a5a02f11525f1f0b0411d8