gitignore, clean cached files

Add comprehensive gitignore for Python projects. Remove accidentally
committed __pycache__ directories.

.gitignore

@@ -0,0 +1,53 @@
+# Byte-compiled / optimized / DLL files
+__pycache__/
+*.py[cod]
+*$py.class
+
+# C extensions
+*.so
+
+# Distribution / packaging
+.Python
+build/
+develop-eggs/
+dist/
+downloads/
+eggs/
+.eggs/
+lib/
+lib64/
+parts/
+sdist/
+var/
+wheels/
+*.egg-info/
+.installed.cfg
+*.egg
+
+# Virtual environments
+.venv/
+venv/
+ENV/
+
+# Testing
+.tox/
+.nox/
+.coverage
+.coverage.*
+htmlcov/
+.pytest_cache/
+.mypy_cache/
+
+# IDEs
+.idea/
+.vscode/
+*.swp
+*.swo
+
+# OS
+.DS_Store
+Thumbs.db
+
+# Project-specific
+benchmarks/
+*.db