This PR adds a detailed Configuration.md document that comprehensively
explains the Compiler Explorer configuration system. It covers:
- Configuration file structure and hierarchical loading
- Property types and automatic conversions
- List separators and specialized formats
- Group inheritance and compiler configuration
- Variable substitution mechanisms
- Advanced features like remote compilers and property debugging
Additionally, it updates all related documentation to reference this
central document for configuration details, reducing duplication and
ensuring consistency.
This document will serve as the foundation for future configuration
system improvements by providing clear documentation of the current
implementation.
