Enhancements and Clarifications

Made an update with a bunch of cool stuff.
Can't think of what to add next, so this'll probably be it for a while.

Every entity that has usable ExtraInfo should now display/work properly.
You can edit multiple entities at once.
Zoom has been improved, and added to the attribute editor. (latter a request by DT)
Screen preview exists now. (request by DT)
A few minor code refactors.
Manual.md has been expanded.