Add a source function to pull code into an empty environment

[MKatz-DHSC]

Code should be as follows:

source_env <- function(file, local = NULL, ...) {
if (!is.null(local)) {
stop("source_env() does not take a local argument.")
}
env <- new.env(parent = baseenv())
source(file = file, local = env, ...)
return(env)
}