Add dynamic node api

Closes #322
- nodes modules can be installed/removed dynamically at runtime
- nodes can be enabled/disabled
- onpaletteadd/onpaletteremove api added to node definitions
- initial implementation of nr-cli

.gitignore

@@ -6,3 +6,4 @@ flows.backup
 nodes/node-red-nodes/
 .npm
 /coverage
+.config.json