cleanup
Change map from V->F->bitmap to F->V->bitmap
Helper method to get all asserted bit map.
extract Bitmap functions into an interface.  Create a segmented bitmap to control memory usage for empties.
on the way toward a N based Trigram.
slice filter introduction
test for previous.
add isEmpty() to IBitmap interface
implement Trigram.contains(String s)
get trigram indexes working.  This required messing with the KeyHashObserver interfaces (these will change anyway).