dox and memory fixes for ode

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@17968 b5f69653-2bf5-0310-8201-b0dafb8e1405
Fix nightly acceptance for r17957 (LUT change) #1795

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@17970 b5f69653-2bf5-0310-8201-b0dafb8e1405