method tooltips polishing

Fix: method tooltips are now much clearer, especially when the method lacks a description

Previously, a method's tooltip was this format:

    {name} :: {docblock/description}

If the method lacked a description, then the tooltip would look like this:

    {name} ::

which looks very very odd!

This patch changes the tooltip to look like this:

* {name}()
* {name}() :: {docblock/description}

with the second format used only if the docblock contains a description.  This makes the tooltip look a bit better imho.

This patch also moves the sidebar method template out into its own XSL template.  This will make future customisation much easier to do, and reduce the risk of regressions as the sidebar gets polished further.