Provision configuration dotfiles everywhere

Summary:
Currently, the devserver role offers an unit "userland-home" to provision
dotfiles. It's not really convenient when we login to another server,
without any shell configuration.

For a better ops experience, this change offers two layers:

• core/userland-home: provisioned to *every* server
• devserver/userland-home: extra files for devserver role

In both cases, files are only propagated if the user has access to
that machine, through a node > forests > groups resolution.

Provisioning dotfiles for dereckson account.
Consolidating tmux configurations.

Test Plan: zsh on Dwellers and a FreeBSD prod machine

Reviewers: dereckson

Reviewed By: dereckson

Differential Revision: https://devcentral.nasqueron.org/D3011