fixing the problem when retrieving values in ArrayHashMap using the
method get(Object) can cause ArrayIndexOutOfBoundsException when the map
is being modified (previous code to avoid this did not work)
make sure the timer in CachedTimeThread goes monotonically to prevent
negative measurements
Revert "experimental: checking if produced conclusions are absent / present in context when preforming saturation for addition / respectively deletion"

This reverts commit 17d89c9318ef512fa993ef775db4543efa2f67ad.
Merge branch 'backport'