Investigate support for 3rd party JS libraries

Research if and how we should support 3rd party javascript libraries from QML.

JavaScript libraries may attempt to do things not allowed by the QML JS environment. For example:

Modify native objects:

• http://sugarjs.com/
• http://www.datejs.com/

Modify the global object:

• http://www.diveintojavascript.com/projects/javascript-sprintf
• http://documentcloud.github.com/underscore/

Many libraries seem to be looking for either a browser environment or a CommonJS-like environment:

• https://github.com/willconant/flow-js (CommonJS "exports" or "window" for browser)
• http://persistencejs.org/ (CommonJS "exports" or "window" for browser)
• https://github.com/caolan/async (CommonJS "exports" or "this" for browser)
• https://github.com/michael/data (CommonJS "exports" or "this" for browser)

In some cases, existing libraries can be made to work with code like:

var window = {}
Qt.include("persistence.js")

Possible solutions:

• Many libraries introspect their JS environment and tweak their code to cater for different environments. We could offer a standard way to identify the QML environment, allowing libraries to tweak themselves to our environment as well
• We could consider introducing a new pragma, or allowing ".pragma library" imports to do special things (e.g. have their own (private?) editable global object)
• A pragma that bootstraps some sort of compatibility layer (like Envjs)

Other notes:

• There seem to be a particularly large number of libraries tailored to node's JS environment: https://github.com/joyent/node/wiki/modules, though it isn't immediately clear how many would also be relevant to QML.