Thorsten (et al) I'd apprecaite your feedback on this patch revision...
1) moved the location of the variables file to ./build using a deep ../../ path ... i didn't change the forrest.properties to do this, because I wanted to keep the catalog.xcat where it was since that seems to be standard.
2) from a clean check out "ant init-forrest-entities" is now a prepreq for forrest to run properly, otherwise the XML doesn't validate because the entities can't resolve. most of hte core ant tasks take care of this via dependencies.
a couple of notes about the specifics...
a) i used the "specversion" since it's the most precise of our version numbers, it contains the datetime of dev builds, and is the number you would expect for official builds
b) i tried to make the entity name consistent with the property name so that if someone smarter then me knows a way to get ant to dump all properties using a <filterchain> we can refer to any ant properties as entities not just solr.specversion
c) if committed, Website_Update_HOWTO needs note about "ant init-forrest-entities"
d) if committed, HowToRelease needs updated to indicate that the docs on the branch need regenerated/commited after building/testing the code sith specversion set, but before packaging.