Help: Update 3.1 release notes for dropping of FindITK and FindVTK

The changes made by commit v3.1.0-rc1~46^2~1 (FindITK: Drop this ancient
compatibility module, 2014-10-02) and commit v3.1.0-rc1~46^2 (FindVTK:
Drop this ancient compatibility module, 2014-10-02) need to come with
release notes explaining that the modules were dropped.  Also remove a
release not related to an update made to FindVTK that was never
released.
Help: Wrap long lines in pre-formatted documentation blocks

Help format the blocks better for display without a wide screen.
Merge branch 'doc-FindITK-FindVTK-relnotes' into release
Merge branch 'doc-formatting' into release