omero: Cpp: Document FindIce changes

- Document FindIce cmake options
- Replace SLICEPATH with ICE_SLICE_DIR
- Remove documentation obsoleted by Ice autodetection
omero: Cpp: Document SLICEPATH workaround
omero: Cpp: Correct cmake link
omero: Cpp: Mark up cmake as a program
omero: Cpp: Reword version restrictions
omero: Cpp: Remove ICE_HOME from examples
omero: Cpp: Remove double space after period
Make Ice 3.5.1 default version
Use new latest/product5.1 redirects across the board
Merge pull request #938 from rleigh-dundee/cmake-ice

omero: Cpp: Document FindIce changes
Merge pull request #943 from hflynn/ice-version

Make Ice 3.5.1 default version
Merge pull request #944 from sbesson/latest_redirect_5.1

Use new latest/product5.1 redirects across the board