Shared env at NCSA migrated to Rubin Env 0.6

The shared stack on NCSA machines has been migrated to Rubin Env 0.6. The stack is available at the standard path of /software/lsstsw/stack and has w_2021_21 installed in it. The previous installation (with previous weeklies is available at /software/lsstsw/stack_20210415.

With this installation we have added testdata_ci_hsc, testdata_ci_imsim and testdata_decam as declared packages. This means you can set up the packages by typing setup testdata_ci_hsc and the shared copy of this data will be setup for you. Please note, this is not a pinned version. If someone adds or removes something from these repositories it will be reflected for everyone who has these packages setup. Currently these packages are refreshed from git each night.

This is no different than the current situation with people directly setting up these packages with -r except we hope that it makes the shared resources easier and more discoverable.