Add kicad_auto container 'flavor' and 'tag' to env variable

[hpopols]

It could be nice to have the version & flavor of the kicad_auto image used in an environment variable to be later used in a worksheet and other outputs.

The idea is the same as the kicad version displayed in the default worksheet but also would help to promote/cite this great software.

What do you think?

[set-soft]

Looks like a good idea.
I'm doing some experiments with the dev images.
I found that for the tag is much easier to use a file, I'm using /etc/kiauto_tag
For the full/basic flavor I'm defining the KICAD_AUTO_FULL environment variable, full images have it defined as 1, not defined for basic images.

[set-soft]

Ok, and now should be propagated to all images ...