Implemented a new version of the mutable HashSet

It is the first step in an attempt to improve performance of the mutable Hash-* collections family. This implementation based mainly on the stock JDK HashSet with some improvements: a bucket with a single element represented as the element itself, a bucket with more than one element represented as a balanced tree
Add caliper benchmarks for new HashSet
Add a script for running caliper benchmarks

Currently the scipt stops after benchmarks build.
Fix the caliper benchmarks build
Modify run-caliper-benchmarks script
Remove from the caliper benchmark script all the Git manipulations
Add actual caliper benchmarks run command to the script
Fix caliper benchmarks run script
Use new HashSet as the default implementation of mutable set

Now we can test our implementation against scala partest suite