Inconsistency in escaping special characters + - % & _ in page selection methods

[Technical-13]

Feature summary (what you would like to be able to do and where):
From my understanding the following characters are currently escaped:

• & like <&>
• _ like [_]

From my understanding the following characters are NOT currently escaped:

• % ...because it "will break much more uses so will be done differently"
• + ...could be a valid character that's also used for catheadings
• - ...could be a valid character that's also used for notcatheadings

Use case(s) (list the steps that you performed to discover that problem, and describe the actual underlying problem which you want to solve. Do not describe only a solution):

• The first two are inconsistent which just makes more work for users of the extension to remember "what characters do I use to escape this special character" because there's no consistent pattern like always use \ or % in other pattern matching schemas.
• As for the other three that aren't yet escaped, I edit on gaming wikis that are currently running DPL3 and on one of them we're considering updating to DPL4. We have a lot of categories like +25% special effect items and -10% special effect items where not having +, -, or % may be an issue.

Benefits (why should this be implemented?):
A consistent uniform method of escaping special characters will produce more accurate results that match user expectations by reducing human and processing errors.