- remove the old LGPL license headers from all files in Spack
- add SPDX headers to all files
- core and most packages are (Apache-2.0 OR MIT)
- a very small number of remaining packages are LGPL-2.1-only
- Versions before 2.5.2 suffer from a serious security problem
(https://nvd.nist.gov/vuln/detail/CVE-2018-12021). Deleted all
versions prior to v2.5.2.
- Update homepage (looks like singularity's going Freemium).
- Use release tarball instead of automagically generated archive
tarball (digest values are more stable).
- No longer need autotools for released versions, just @devel.
- Install needs to be single-threaded, otherwise when installed as
root the various 'chmod' operations race against the copies.
* singularity - added master branch as this has latest fixes - 2.4 does not compile on centos 6 without use of this branch
* renamed to develop
* added master branch properly
