add pdb style 'commands [bpnumber]' to break point

[pzi123]

One of the most useful features of a source debugger is ability to execute debugger commands as part of the break point processing. This is implemented as part of the pdb debugger with 'commands [bpnumber]' command. This can be used to print an expression with pp and then issue 'continue'. This works as the alternative to planting print statements directly in the code.

In pdb we issue 'commands 1;; pp spam;; continue;; end' to bind these commands to break point 1. Please consider adding it to the break point options alongside 'Condition'.

Now if all that could be saved in the ~/.pdbrc style file so it can be reused between runs it would be wonderful.

[inducer]

I'd be happy to consider a PR to that effect.

[inducer]

(But I don't have the spare cycles to do it myself at the moment, unfortunately.)