-fixed bug(s) in rex where commands like setenv("FOO_${BAH}", "EEK") are accepted,
 but the new value is not tracked because the key is not expanded
-fixed bug in rex where legit bash syntax ${!FOO} was causing the NamespaceFormatter
 to fail.
-fixed bug in rex where it was not possible to iterate over 'env'.
-fixed bug where accessing an env-var like "env['FOO']" failed if it was
 not accessed earlier like "env.FOO"
-improved rex exception printouts, added non-catch config setting for debugging
-added timing tracking, for debugging purposes