Incorrect encoding and decoding of symbolic names in scaladoc links

[szeiger]

Symbolic method names such as https://github.com/sbt/sbt-sdlc/blob/4b27e22299fe873ded8d451fe6d3ac3995a55ab7/src/sbt-test/sdlc/simple/src/main/scala/com/example/Main.scala#L8-L13 are not encoded and decoded properly by scaladoc.

For example, using the permalink next to method " actually links to method %22 (which happens to be the url-encoded version of ". All method names should have a consistent encoding and decoding applied. Ideally this should be done to the individual names before constructing signatures, otherwise there will still be ambiguities between signatures such as `x` () and `x()`.

Verified with scaladoc versions 2.11.12, 2.12.8 and 2.13.0.