Sitemaps correctly filter draft posts

fixes #4612

- adds missing line of code to remove draft posts
- adds tests to check drafts aren't added
Merge pull request #4614 from ErisDS/issue-4612

Sitemaps correctly filter draft posts
Update technical details version numvers

They were a bit dated. Nothing else.
Added Highlight to Markdown Help
Merge pull request #4617 from dbalders/markdown

Added Highlight to Markdown Help
Add Tag Meta View

Closes #4509, Closes #4615

- Adds meta title & meta description input fields
- Autosaves meta data
- Shows SEO preview (falling back to tag name & description if meta not supplied)
- Adds `type="button"` to delete button (which closes 4651)