added code to compute plane ray intersection parameter + generalized intersection to use the precision if the plane (not just float)
added code to compute plane ray intersection parameter + generalized intersection to use the precision if the plane (not just float)

git-svn-id: 0a20d38d1bcdb3210d244a647211d61b0aabf366@86 5b8196f7-c1c0-4be6-8b13-4feed349168d

BlueBrain/Tuvok,BlueBrain/Tuvok,BlueBrain/Tuvok