Combinators for work with effectful programs (those use @Cms and @Sub).
TODO: add some great docs.
Adds an another init to the "oneOfInits+[orInit]"-chain.
Updates one of two submodels using corresponding subupdate function.
Combines two subscriptions.
Combines two inits models to selector and list of paths.
This is a first step in the "oneOfInits+[orInit]"-chain.