Use IDENT for keys in node props

[AvitalTamir]

Due to a historical mistake, keys in node properties are associated with JSONPATHs in the parser. They should actually be IDENTs since we only allow a single level (of either labels or name).

Slashes and dots must be legal. Labels often contain dots (.) and forward slashes (/).
These are legal in Kubernetes and are common in the community (i.e. somecompany.com/status: "ok") - but are currently not parsed correctly by Cyphernetes.