docs: design notes for a Redfish/IPMI BMC driver

No code yet. The README explains why one Redfish driver with vendor quirk
modules beats a Supermicro-only IPMI driver, and keeps IPMI over LAN as a
read-only fallback. docs/ holds a draft for a new ManagementController
role base in napalm-device-types, the getter-to-resource map, the first
test device (Supermicro X10DRL-i, Redfish firmware 3.91), the security
points (IPMI RAKP hash disclosure, power control, credentials) and the
test plan with DMTF mockups and fixtures to record.

.gitignore

@@ -0,0 +1,7 @@
+__pycache__/
+*.py[cod]
+*.egg-info/
+build/
+dist/
+.venv/
+.pytest_cache/