Prepare the existing code in the dev branch for merging to master

[pronobis]

The code already in dev should be reviewed by the original authors to make sure it is of sufficiently high quality for merging into master. Basic clean-up should happen for existing features, but no new significant features should be introduced (unless they are required as part of the cleanup).

When this issue is closed, the dev branch will be merged into master.

New features potentially targeted for the release, should be sent as a PR against dev, and added to the libspn-release "needs triage" column. These PRs will either be merged to dev before it is merged with master, or more likely will be re-based against master after the merge.