Changes:
- http request node passes on request url as msg.url
- handle config nodes appearing out of order in flow file - don't assume they are always at the start
- move subflow palette category to the top, to make it more obvious
- fix labelling of Raspberry Pi pins
- allow email node to mark mail as read
- fix saving library content
- add node-red and node-red-pi start scripts
- use $HOME/.node-red for user data unless specified otherwise (or existing data is found in install dir)