More flexible URL syntax

[Ralf Lämmel]

We have some "strange" feature names in MetaLib:

• AST+ (or AST^+)
• AST- (or AST^-)
• Interpret^O

If we wanted to have a direct mapping to 101wiki entities, we would need URLs such as:

https://101wiki.softlang.org/AST+
https://101wiki.softlang.org/AST^+
https://101wiki.softlang.org/AST-
https://101wiki.softlang.org/AST^-
https://101wiki.softlang.org/Interpret^O

Would it be legal to use them?

Currently, https://101wiki.softlang.org/AST^- definitely does not work because "-" is rewritten away.

[Ralf Lämmel]

softlang/metalib#17