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That can be one or more of:
- New
- New version
- Fork

It depends on the asset type.

Until now, only the prefix path was passed around. However.
there are cases where more information is needed like for
example the current user when creating new assets.

This commit also fixes the parameter handling of the editor
command which was duplicating what was already done by
beat.cmdline.

Depending on the asset type, it can be:
- A new asset from scratch
- A new version of an asset
- A fork from an asset

**WARNING** not all asset types can be forked.
This will fail accordingly.

**WARNING** not all asset types have version support.
This will fail accordingly.

**WARNING** not all asset types can be created from scratch.
This will fail accordingly.

This is because the support for ProtocolTemplate comes with this
version as well as better support for creating new assets.

This wasn't following the asset name properly

The prefix path is going to be used by all editors.[widgets] Remove field and test_editors

These were serving demonstration purposes. They are not needed
anymore.

This will enable users to copy elements of the v1 implementation.

Currently unused

Fixes #183

This button and its associated layout are created many times.
Factor this in one function.

Part of #183

In case of buildout development setup.

Ensure that:
- If type is different, signal is emitted and type properly changed
- If type is same, nothing happens