Create a copy of the previous flow file (flow.previous) before each deploy
closes #184
In case of emergency you can now find the previous flow file before you hit 
deploy in a file called flow.previous . As indicated it is the flow that was 
running prior to you hitting deploy...
change preferred name of backup file to flows.backup
(even if it is the previous version :-)
relates to Issue #184
Reduce GPIO setup on Pi node to try to make it play nice with other peripherals
Refactor editor.js to reduce duplication of editor setup

Part of #93

This reduces the duplication in code that creates the both the normal-
and the config-node dialogs.

It also identifies the key points that credentials handling should
be introduced.
Fix flow backup for first run, add tests