Add ziplistDeleteRangeFromOffset

Added `ziplistDeleteRangeFromOffset` allowing to remove more than one entry from ziplist starting from a given entry in the ziplist.
Changed `ziplistDelete` to return result from `ziplistDeleteRangeFromOffset` call. 
In addition, replaced every `ziplistDelete` double-call to a single `ziplistDeleteRangeFromOffset` call.

These changes were made due to a "TODO" request in the code.

Tests - I have run `make test` to approve that my changes haven't caused new problems.