Add upgrade notes

UPGRADE_GUIDE

+# Upgrade Guide
+
+# Pre-Release -> 1.0.1 
+
+In the pre-release version of Polaris, the paths for the Docker volumes were different; when upgrading, make sure that the path for the Postgres volume no longer includes "production".
+```
+    volumes:
+      - ./mongodb_data:/data/db
+     ...
+    volumes:
+      - ./db:/var/lib/mysql
+    ...
+    volumens:
+      - ./database_analytics/production:/var/lib/postgresql/data
+```
+Additionally, the schemas in Polaris have changed — the Rights Engine updates these automatically, but you may want to manually adjust the JSON schema. You can find guidance on this in the documentation: https://polaris.pages.rwth-aachen.de/rights-engine/provider_schema/#migrating-from-an-older-version-prior-to-101
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