Re-order fields, set Source first, then Target

Problem/Motivation

Usually the order of parameters with a source and target (for example rsync) is in that order, perhaps it could also be here, where they are reversed, which seems not intuitive to me.

Proposed resolution

Reverse the order of "Source" and "Target" in the field updater creation form, to this order:

• Label
• Entity type
• Bundle
• Source field
• Target field

The same could apply to the list of field updaters on the Mapping page, they could be updated to this order:

• Source
• Target
• Value source

Remaining tasks

Set Source first, then Target?

User interface changes

API changes

Data model changes