Apache Axis2/C 2.0.0 site — replace 2009 site with mkdocs

First site update since 1.6.0 (2009). New site built with MkDocs
Material theme, documenting HTTP/2, JSON-RPC, Android support,
weak symbol registry, MCP protocol, and security (mTLS).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>