Improves PO controller from UX perspective

[DidierRLopes]

This PR does the following:

• Improve UX of PO menu to be more intuitive
• Commands unavailable when portfolio not loaded
• Fix reset to re-load portfolio and re-load params
• Remove add/rmv commands
• Allow -h in load and file cmd

[JerBouma]

@DidierRLopes If you haven't already, could you also look into this:

/portfolio/po/load & file do not show a help dialogue with -h flag

(🦋) /portfolio/po/ $ load -h
usage: load -f FILE [FILE ...] [-h]
load: error: the following arguments are required: -f/--file

[DidierRLopes]

@DidierRLopes If you haven't already, could you also look into this:

/portfolio/po/load & file do not show a help dialogue with -h flag

(🦋) /portfolio/po/ $ load -h
usage: load -f FILE [FILE ...] [-h]
load: error: the following arguments are required: -f/--file

Yup, let me do that now :)

[DidierRLopes]

@DidierRLopes If you haven't already, could you also look into this:
/portfolio/po/load & file do not show a help dialogue with -h flag

(🦋) /portfolio/po/ $ load -h
usage: load -f FILE [FILE ...] [-h]
load: error: the following arguments are required: -f/--file

Yup, let me do that now :)

Should be done now @JerBouma

[JerBouma]

Looks good to me :)