Correctly format commons links with spaces

Spaces should be replaced with underscores in URLs, underscores should be
replaced with spaces for link texts, plus signs should stay what they are.

Using Title here is probably not completely sane since it takes the local
configuration into account. It works, though.

Bug: 61738
Bug: 45046
Change-Id: I4cac81188e5a09bd1a4cbf5ccdf3c579fce9821a
(cherry picked from commit 24984f6f2e13c5e006c4f9ec1c57c0a194845a6a)