Top-level metapackages' versions should be memorable

[mjuric]

In EUPS world, we distinguish an release from others by it's EUPS tag (e.g., v10_1).

Conda has no concept of release tags, but we could (maybe) approximate this by making the top-level metapackage versions be equal to the release number (e.g., lsst-distrib-10.1 [*]).

h/t to Chris W. for the idea.

[*] Actually, it would actually be lsst-distrib-0.10.1 due to "version minification" (as described in README.md).