Extend link view to take a label

[jdlrobson]

Sometimes it is useful to define the label for a link your self for instance

<<view title link>>

for a tiddler called bar currently creates a link with label "bar"

This patch recognises an additional parameter as the real label. e.g.

<<view title link link>>

would create a link to the tiddler "bar" but the label would say link.

This becomes particular useful in template #1286 and #1413