chore: drop the core to 0.1.0 and restate the stability promise

The API has one set of consumers and no outside users, so declaring 1.0.0
with a stability guarantee was premature. Until 1.0.0 any minor bump may
reshape the API; the written guarantee starts there. Plugins pin 0.1.0.

nemoRepoCore/version.py

@@ -1,6 +1,6 @@
 """Version of the core library and the compatibility check plugins call."""
 
-coreVersion = "1.0.0"
+coreVersion = "0.1.0"
 
 
 class CoreVersionError(RuntimeError):