Add sysexec

Adding in ability to call a system proc from the core engine, using 1 of 2 DSL statements.
1. I execute system process "(.+?)" => which will call any system process checking the return code.
2. I execute a unix system process "(.+?)" => which will call a shell command passing the string to the shell.

The first option does not allow pipes or redirects, the second option does, however is restricted to unix shell.