action=jadecreateorendorseproposal
1. The entity page doesn't exist at all. (comment: `/* jade-createandendorseproposal */`)
* Create the page, create the relevant proposal
* Add an endorsement from the user.
* Set the preferred bit to point to the new proposal.
2. The entity page exists but no matching proposed label and the user has not already endorsed a proposal for this facet (comment: `/* jade-createandendorseproposal */`)
* Create the relevant proposal
* Add an endorsement from the user.
* If another proposal exists for the target facet: Raise a `endorsingnonpreferredproposal` warning and leave the preferred bit alone
* Otherwise, set the proposal bit for the current proposal.
3. The entity page exists and there's a proposed label with matching data. `/* jade-endorseproposal */`
* Add an endorsement from the user.
* Raise a warning saying that the proposal's "notes" were not overwritten
* If the proposal is not preferred: Raise a `endorsingnonpreferredproposal` warning and leave the preferred bit alone
4. The user already has an endorsement for this facet but it is for a different proposal.
* If the target `labeldata` is not represented in any proposal: Create the proposal
* Move the user's endorsement to the target proposal and update the `endorsementcomment`. `/* jade-createandendorseproposal */`
* Otherwise, if the target `labeldata` exists, just move the endorsement. `/* jade-moveendorsement */`
* If the proposal is not preferred: Raise a `endorsingnonpreferredproposal` warning and leave the preferred bit alone