Opening and Saving of Projects

@linusha is already working on this.

Since Feb 10, 2023.

# Opening of Projects

When a Project is being opened, the following happens:

- [x] run _version binding_
- [x] ensure that, if a remote is present, we have the latest version pulled
- [x] open a lively.next session with the project loaded as a package

It should be possible to work without any knowledge of git as long as possible!

In case the offline mode is enabled, we:
- [x] create the local commits anyway

The dropdown of the open button allows a user to
- [ ] circumvent the git sync
- [ ] open a different workspace than the default workspace

# Storing of Projects

There exists a save button in the top bar, which also has a dropdown.

- saving will
- [ ] serialize the currently open workspace
- [x] stage, commit and push all changes in the current project
- [x] the commit message should make clear how it was created

The Dropdown allows to

- [ ] just store the workspace
- [ ] just store the workspace under a different name
- [x] open a lively shell

# Version Binding

Version Binding is a mechanism that allows us to indicate that projects/playgrounds belong to a specific version of the lively core.
This mechanism is run before opening a project/playground.
For projects, we indicate the matching core version by the commit hash of the core repo in the "lively" object of a projects `package.json`.
For playgrounds, we indicate the pinned version in the `package.json` of the package of the world.

The mechanism is as follows:

- If the version is ahead the current lively.next
- [x] the load is canceled
- [x] notifying the user to update the system to be able to load that version.
- [x] a button is presented that
- shuts down the server,
- stashes the changes in the core (if there are any)
- pulls the latest version,
- runs install and
- starts the server again
- If the version is behind the current lively.next the load is performed and
- [x] upon completion the user is prompted to confirm that the version tag of the project/playground be updated.
- If that is declined, the session is closed again.
- If confirmed the session continues.
- If the version matches the current lively.next everything loads as normal.