Clean RecCard

[cydanil]

This is a follow-up of #130.

Here, we're cleaning the RecCard class by adding annotations, removing unreachable code, and modernising properties decorators.

rec_gui, formely rg, is never None, a fact that was highlighted by the fact that the conditional import doesn't even work, thus removed.

[maweki]

First of all, good work! Also on the set_ and get_ translations.

Second: Are all these attributes to be "written" by other methods? Some of these look like they should be hidden via double-underscores, others are functional or read-only and could be properties. Do you have any deeper insight?

If we can slim the interface down even further, it would be great.

[cydanil]

I was not keen to tackle that, but doing so revealed that RecCard.conf is a leftover from a previous architecture, and can be removed!

[cydanil]

I spoke too soon: RecCard.conf cannot be removed at the moment without introducing ugliness elsewhere, at least in GourmetRecipeManager, line 443:

gourmet/gourmet/GourmetRecipeManager.py

Lines 439 to 444 in 40e911a

	def quit (self):
	for c in self.conf:
	c.save_properties()
	for r in list(self.rc.values()):
	for c in r.conf:
	c.save_properties()

The rest is okay, though

[cydanil]

If there are no further comments, I'll merge in a few hours, thanks!