Optimise epileptors by avoiding sub-expressions recomputation. dfun 1.4 times faster.

git-svn-id: https://repo.thevirtualbrain.org/svn/tvb/trunk/scientific_library@6945 1c0e02f0-7929-43c0-8fb3-3293bf43b0d1
TVB-1661 renamed operation field

git-svn-id: https://repo.thevirtualbrain.org/svn/tvb/trunk/scientific_library@6950 1c0e02f0-7929-43c0-8fb3-3293bf43b0d1
Merge branch 'trunk' of https://github.com/the-virtual-brain/tvb-library into trunk