Development version

• Add support to translation of SMOOTH functions from Vensim & Stella.
• Add sd_sensitivity_run(). This function supports parallelisation in Unix-based systems.
• Add flexibility to read_xmile() by allowing the user to override values of constants and initial values of stocks.
• Add sd_constants() and sd_stocks() to summarise model’s information in data frames.
• Add stan_ode_function()
• Add stan_data()
• Add support to unidimensional vectors in Stella.
• Support the translation of the following math functions: ABS & SQRT.