Reduced redundancy in Elements handling

[Raijinili]

• Preparation for changing element names in the editor. It should no longer look up elements by editor name at any point, so the editor name can be changed.
• Refactor enum enumeration throughout. (Newer .NET versions have Enum.GetValues<EType>, which should replace that.)
• Fix reversed Element read in XML. (Not that it's used.)
• Removed Elements redundancy.
• Removed some Utilities methods which were in LINQ already.

Warning: You may decide to change the names of my new classes.

Warning: The old Utilities.ToList used to return a readonly list. But since the way it was used (i.e. didn't save to a readonly-typed var) doesn't give a compiler warning, who cares? Besides, I bet it was misused and caused crashes at some points.

[Glain]

Handled differently with commit ff3d0ca.