Speed-up/Cache loadNamespace()

Thank you Serguei and Gabor.
Great suggestions.

If your R scripts contain "stop()" or "q('yes')" or any other error, it
will end the Rscript process. Kind of watch-dog can be set for automatic
relaunching if needed.

It should be possible to change the error handling behavior.

From within R:

options (error = function () NULL)

Or something better...

Also, it may be desirable to wipe the global environment (or parts of
it), after each script:

    remove (list = ls (envir=.GlobalEnv, all.names=TRUE) )