Add some unified way to choose a program in useful scripts

[betaveros]

There are a lot of useful scripts that have some program ID hardcoded into them that they operate on, or ask for a program or program ID from the user in ad hoc ways. It should not be too difficult to make a more unified and user-friendly way to choose a program, so the user could enter an ID or a program name, or even choose from a list of likely programs generated with current_program or similar logic. We could put a utility function in shell_utils.py.