Jasonette Extension Workflow and Maintenance

Now that people contribute and start to develop extensions for actions and other things
in Jasonette, we begin to see problems w.r.t. the extension development workflow.

This issue intends to kick off a discussion on the following and other related topics.

**XCode Project Issues**

As soon as more than one developer works in the main repository, changes in the XCode project files start to become an issue. While these files are text files in principle, merging them is a PITA.

Also it's not immediately clear what changes should be merged.

- How do we manage XCode project files and work spaces?
- Do we need to git-manage them at all?
- How do other successful projects in the same area solve this problem?

**Extension Maintenance**

While the current practice of adding code to the main line of Jasonette is probably OK for now,
not all extensions people come up with are useful or generic enough to warrant a inclusion in the
main line of Jasonette.

- How can we support out-of-repository sharing of extensions?
- Do we need to add special code to Jasonette to support a plugin-like system?
- Are binary frameworks "good enough" and can we use [cocoapods](https://cocoapods.org/)?

The issue names no files, tests, or entry points. Start by reviewing how the XCode project and workspaces are managed, then examine the current extension development and maintenance approach. Done requires an agreed workflow for project files and a decided approach for sharing and integrating extensions.

Written by the indexing model from the issue text.