Added initial CommonJS support

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PR as discussed in #267

This implements a CommonJS module system for loading libraries.

• requiring and exporting work just like you would expect
• this implementation DOES provide isolation from libraries' adding to the global namespace, by loading each library into a script engine with it's own context, then referencing the exports inside it
• I have not added a version of log.js (as in Initial contribution core/log.js #268), although this is trivial to port
• I have removed the requirement for defining 'me' as it's incompatible here, and simply used the uuid

I do believe that pulling the loading engine up into OH code would be better, but agree that we should wait for JDK9/ES6 before we do this (although if it really drags on, I may do it). Either way, this PR means that all library code written now would be compatible with that future.

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Oh, and one other thing as mentioned elsewhere: this really shows that utils.js should be broken up into logical parts. It seems to cover a little bit of everything. For example one of the first things that I'd do is move getItem, sendCommand, postUpdate to items.js (#266)

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After looking at this, I have discovered that there is a problem:

• Isolation happens by loading scripts into a new context, in a new engine
• This generally works fine
• However scriptExtension.importPreset isn't present in these contexts
• I can however pre-load all the properties from these and supply them into sub-contexts via synthetic modules (then they use via require('RuleSupport') for example).
• This appears to not work well however, causing issues calling functions back in the parent context and marshalling arguments through
• Ultimately, I think providing isolation this way is too complex and needs to be done in the above OH layer.
  I'll close this PR and open a new one without isolation.