Avoid text substitution in EditorHelp messages

[timothyqiu]

String There is currently no description for this %s. exists for different method types. Other types of elements have dedicated versions of this string without substitution.

This substitution may bring difficulties for localization. e.g. For languages that have gender for nouns. So I turned it into individual strings.

p.s. Also removed the unused EditorHelp::Page enum.

[MewPurPur]

Seems unnecessary to have more code for a placeholder we ultimately want to erase from existence. Can't we just use "This description is currently missing."?

[YuriSizov]

@MewPurPur There is nothing wrong with being verbose and less repetitive, and we'll always need these placeholders as long as the project is developed :)

[YuriSizov]

Thanks!