Draft: Add streaming functionality

This merge request adds advanced interactive features to a Java employee management system. The main changes include:

New Interactive Capabilities: Added a command-line interface that lets users dynamically query and analyze employee data in real-time, with support for complex filtering using method chaining (like "find all engineers hired after 2020 with salaries above $70k").

Advanced Analytics: Introduced comprehensive statistical analysis features including salary percentile calculations, department comparisons, promotion candidate identification based on tenure, and performance metrics. The system can now calculate things like median salaries, standard deviations, and identify high performers.

Enhanced Documentation: Updated the README to showcase three different demo modes - the original basic demo, an interactive stream operations demo, and a full command-line interface. Added detailed setup instructions and examples of the new features.

Query Builder System: Created a flexible query builder that allows users to chain multiple filters together dynamically, making it easy to build complex searches without writing code.

The changes transform a simple demonstration into a comprehensive HR analytics tool while maintaining the educational focus on Java 8 functional programming concepts like streams, lambdas, and collectors.