* More optimized container suite that greatly improves build time.
* Added static Debian packages for Devel::Cover to reduce build time.
* Add deprecated state for containers. Deprecated containers may only be used to build packages.
* Remove Debian 8 from CI because it does not provide additional coverage over Ubuntu 14.04 and Ubuntu 16.04.
The options accommodate systems where CAs are not automatically found by IO::Socket::SSL, i.e. RHEL7, or to load custom CAs.
Suggested by Scott Frazer.
* Combine hardlink and non/compressed in synthetic tests to reduce test time and improve coverage.
* Change log level of hardlink logging to detail.
* Cast size in S3 manifest to integer.
Refactor storage layer to allow for new repository filesystems using drivers. (Reviewed by Cynthia Shang.)
Refactor IO layer to allow for new compression formats, checksum types, and other capabilities using filters. (Reviewed by Cynthia Shang.)
