call system process from any engine

Ability to call the system process from any engine.  WIP.
Working on scala piping commands.
Adding in capability to call system processes to execute scripts.  Currently it supports unix scripts and general calls to exec shell.  However with the later, no pipes or redirections are permitted.
Merge remote-tracking branch 'origin/add_sysexec'
add unit tests for sys process support

After merging in system process support, needed to add some eval engine
unit tests.