Revise for 9.0.0 API

Revise for Mathics 9.0.0 release

• Add mframe: is like frame but for Mathics3-related frame motion
• Add mprogram: is like program but for Mathics3-related frame
• Add abort: Aborts current Mathics3 command

A sad day in the U.S of A.

First public release. Add trepan3k debugger command functions

• mathics3: Go into a Mathic3 shell
• mbacktrace: backtrace showing interesting Mathics3 frame interpretation
• mup: frame up allowing for jumping to interesting Mathics3 frame
• mdown, frame down allowing for jumping to interesting Mathics3 frame
• printelement: print customized for Mathics3 objects