PR: Move tour images out of _static to ensure they are unique per-version

[CAM-Gerlach]

Pull Request

Pull Request Checklist

• [x] Read and followed this repo's Contributing Guidelines
• [x] Based your PR on the latest version of the correct branch (master or 4.x)
• [x] Checked your writing carefully for correct English spelling, grammar, etc
• [x] Described your changes and the motivation for them below
• [x] Noted what issue(s) this pull request resolves, creating one if needed

Description of Changes

Moves the tour images from doc/_static/images to doc/images so they don't get shared across all docs versions with sphinx-multiversion.

Note: I'll need to fix the images being different when merging to master.

Issue(s) Resolved

Fixes #268

[CAM-Gerlach]

I can confirm this works locally as well as on the preview, but the only way to actually test it on the production branches and confirm thus is to merge it to 4.x and then master, so going ahead with it.

[CAM-Gerlach]

Sphinx-multiversion still is copying the assets from the active branch to all branches, instead of from each branch. Trying to figure out a way around that...