Release for CNW-Grass paper and new model architecture

New features

• Introduction of the hydraulic model implemented for the simulation of the co-regulation of leaf growth by the trophic and water status published by @victoriaacker (see Acker et al. (2026).
• New options to disable soil N and root N uptake equations for coupling with external models (by @GeraultTr, @mwoussen)
• Introduction of the early stages of plant developement (seed germination and growth of the first leaves): not pusblished yet, still under developement (@rbarillot, @mngauthier)
• Refactoring of the whole model structure into a single repository and make it compatible with the Openalea release 3. (@pradal, @christian34, @baugetfa, @thomasarsouze

paper_JXBot_2020

Source codes used for the research article Gauthier et al. (2020)
http://dx.doi.org/10.1093/jxb/eraa276