The craziness of $@ and $* implemented

Introduced a new field part, IFS, which is recognized by field splitting, even inside double quotes.
This is how "$@" is implemented.

Much of parameter expansion with $@ and $* is left unspecified by the spec. Took as rational an approach as could be mustered!
$$ and $! variables

since plush doesn't do background jobs, $! was trivial
getVar refactored