Complete comprehensive tutorials and finalize documentation

Added comprehensive cluster-specific tutorials:

1. SLURM Tutorial (tutorials/slurm_tutorial.rst):
   - Complete SLURM configuration and resource specification
   - Scientific computing and machine learning examples
   - Job management, monitoring, and best practices
   - Monte Carlo simulations and distributed workflows

2. PBS/Torque Tutorial (tutorials/pbs_tutorial.rst):
   - PBS-specific resource syntax and queue management
   - Bioinformatics pipeline examples
   - Array-style processing and resource monitoring
   - Error handling and debugging strategies

3. Kubernetes Tutorial (tutorials/kubernetes_tutorial.rst):
   - Cloud-native containerized computing
   - Custom Docker images and resource limits
   - Microservices-style distributed processing
   - Auto-scaling, fault tolerance, and monitoring
   - Distributed machine learning workflows

4. Updated Documentation Index:
   - Added all new tutorials to main index
   - Proper organization of user guides and tutorials
   - Complete coverage of all supported cluster types

All tutorials include:
- Detailed configuration examples
- Real-world use cases and code samples
- Best practices and troubleshooting guides
- Resource estimation and optimization tips

Documentation is now comprehensive and production-ready for users
working with any of the supported cluster environments.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com)

Author: jeremymanning