Allow entering @, ? and # characters in link references

Right now @, ? and # are special characters (@ is for interwiki links) and thus cannot be used in a link reference.

Here are 2 ideas:

• Add some escape support to allow entering them.
• Instead make the reference a pure reference without additional data added and instead use parameters to specify additional data, for example

  [[reference||queryString="..." interwiki="..." anchor="..."]]