support for use_strict

variable appears unused but results in

ReferenceError: flowfile is not defined

when node is invoked with --use_strict
Serial port select combo-box
Remove rogue console.log
Don't show edit dialog for dblclick-drag
Closes #217
Delay node dropping intermediate messages incorrectly
Prevent accidental edit of nodes
Part of #217
Tweaks to shorten Serialport html names.
and remove redundant code.
Log.addHandler missing its implementation
Function error not recognised as TypeError
Remove console.log in credentials
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
Handle parse errors in template file
Twitter: add rate limit warning
Add comms module
TypeError on debug node
Fixes #223
File In node loses message properties