Initial webpack implementation

[Tyriar]

Part of #158

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@parisk this PR is a bit messy at the moment, let me know your thoughts on the general approach here. Basically the following changes would come with/after this change:

• Builds are done using webpack, the module is built at npm install time and the file that is relied upon is ./dist/xterm.js (see main in package.json)
• Addons will be pulled out into their own repositories and published as independent modules, this means that not all addons need to be loaded at once and are more modular in nature
• We can split out all the different pieces of logic in xterm.js into a well structured tree
• Development is done by running:
  • First terminal: npm run dev to watch/compile sources
  • Second terminal: npm start to start server as before
• Eventually change to exposing the library in an xtermjs object that contains a Terminal object would be preferable particularly for TypeScript as a proper typings file could be written for the library (ie. export { Terminal: Terminal }; vs export Terminal)
• We can start using babel or similar to enable more elegant/efficient syntax without hurting compatibility in the resulting distributable
• We can get rid of the AMD header as it's all handled by webpack
• Allow minification/removal of comments in prod version, pushing the size of the distributable down significantly

[Tyriar]

@parisk any thoughts on the approach? Didn't want to continue until choice of tech, method, etc. was cool.

[parisk]

Sorry for being late here @Tyriar.

I have no significant webpack knowledge at the moment and TBH I am really reluctant to move forward with such a move without laying down first the pros and cons and examining alternatives.

I think that #158 is the best place to make some discussion about our options and choose the one that fits the project's needs better 😊 .

[Tyriar]

Closing as it's stale and going to try a TypeScript implementation.