Add spawning of self-employed villagers

[scrain777]

Plant gathers spawn near plants that can be gathered. The owner is set to working_villages:self_employed, and any player with a commanding_sceptre can interact with them as if the player were the owner.

A few minor corrections also:

• Suppress a warning about access to undefined global variable modutils.
• Bugfix: server crashed under the race condition where a plant was harvested by another entity between a plant gatherer selecting it and digging it.

[theFox6]

Originally I planned to spawn a settlers cart that would be the beginning of a village. But with villagers being spawned independent from villages, hermits and traders could also be distributed around the world.

[sfence]

Originally I planned to spawn a settlers cart that would be the beginning of a village. But with villagers being spawned independent from villages, hermits and traders could also be distributed around the world.

This behavior is disabled by default. So it should not affect villagers spawning in villages later.

[scrain777]

My vision (started before I decided your working_villages was a better base for my work) was a mod that starts as a gatherer and has to learn to create her own tools and learn new skills, eventually forming a community with others that spawned nearby. I think that the ability to spawn could also be a good start towards your vision based around settlements.

[theFox6]

That is a very nice Idea, I am glad to have you in this project. As a collaborator you have the possibility to merge pull requests yourself and to push directly into this repository. I trust you to take good care of the project I started.