Tidy up project

This is a very good utility project, however it could need some polish / tidying up:

* close old and finished project issues, add documentations where applicable (thread safety?)
* fix builder pattern
* return instance from builder
* must the build(Map) be a TreeMap?
* use protected methods instead of private (to be consistent with field access)
* move inner classes, interfaces to seperate types
* possibly tie search type to builder
* no public fields
* remove object input / output stream, or at least move to seperate class
* why read/write fields instead of full class?
* nuke commented-out code
* add code coverage maven plugins (currently at 72%), i.e. jacoco
* add github integrations for security patches (i.e. snyk etc)
* add github integrations for code quality, fix flagged issues
* add JMH module for proper performance comparisons