Added createLogFitsThumb
Modify: createLogFitsThumb: stabilized when very few pixels available
Fix: Statistics.cc: mean not correct
ups: add dependency on sconsUtils for building
ups: now require cfitsio

Not requiring afw, so require cfitsio directly.
Fixed dependency.
  - setupRequired(swig)
  - setupRequired(cfitsio)
  - Removed lsstimport: it seems to me lsstimport is for afw.table.
  - Removed lsst.utils.tests: MemoryTestCase can see only Citizons, methinks.
Merge origin/master
zscale: deal with no valid pixels

If there are no valid pixels, we can set the limits to whatever
we want in order to make an image.
gitignore: catch new test outputs
Parameters are now configurable
Renamed new API's name to createThumbnail().
createFitsthumb() of old API is still kept.
Revised tests & examples
Deleted sRGBScale(LabScale()) because this is nearly the unity function
Add MinmaxScale: map (min, max) to [0, 255] naively
added doc/index.html