#16 Refactoring of layout.xsl

[Hussein Badakhchani]

The Navigation related templates should be removed
from layout.xsl and placed in their own file.

location_tree template is a good candidate for this. Also
location_tree it may be possible to simplify location tree
to use only one xsl:when element rather than one for
each expected view.

As all views now share the same element stucture e.g
<View name="Building"/> rather than <BuildingView> We
might be able to use one xsl:when tag that tests for all
views by their name attribute and selects the
approproate content.