Modules manager

addgateway — Adds dynamically builtin at runtime.
addmodule — Add module to Nelson.
gatewayinfo — Returns information about an gateway.
getmodules — Returns list of modules loaded in Nelson.
ismodule — Checks if a module is loaded.
module.json — module.json description
modulepath — Returns path of a module.
nmm — Nelson Modules Manager.
nmm_build_help — helper's function to build help of an external module
nmm_build_loader — helper's function to build main loader.m of an external module
removegateway — Removes dynamically builtin at runtime.
removemodule — remove a module from Nelson.
requiremodule — Returns an error if module is not loaded in Nelson.
semver — semantic versioner.
toolboxdir — Returns path of a module.
usermodulesdir — Returns path where external modules are saved.