Clean up Metadata menu in showJ

[azazellochg]

Editing, adding and removing metadata should go..

As per JM:

This is the legacy code in the showj that was originally inherited from Xmipp, where some metadata functions were available. ..most of them does not make sense when visualizing objects in Scipion.

[pconesa]

Actually, none of them? Remove disables and remove selection, actually "deletes" the items.

[pconesa]

@delarosatrevin , could you confirm. My doubt is only about "Save state" that I've seen it related to Ctf recalculation?