LinkRenderer: Re-implement noclasses as makePreloadedLink function

LinkRenderer: Re-implement noclasses as makePreloadedLink function

'noclasses' makes more sense as a per-link option rather than an
instance member of the LinkRenderer instance, since it depends entirely
on whether the calling code has preloaded the link classes.

Introduce LinkRenderer::makePreloadedLink() which makes this clear and
requires passing in the classes as a separate parameter. As a side-
effect, due to the way LinkRenderer::mergeAttribs() is implemented, the
'class' attribute will always appear before the 'title' attribute in the
final output.

Change-Id: I0545aa9d7139794bc22f9d3d6d6eccde003b2982