Provide a container factory rather than an immediate global container

I've been running into an issue with electrolyte where the fact that it operates as a global container (cached by node once `require`d) makes it problematic to use when you have one electrolyte project using another electrolyte library as a dependency (since node doesn't guarantee that your dependency won't just use a higher level electrolyte in `node_modules`). So I get collisions on component names, which silently override the earlier ones. It also makes testing harder because I cannot create isolated containers for a given test suite.

No file or test is named. Start by tracing how the package is required and cached by Node, then determine how a factory could create isolated containers; done means separate projects and test suites can use independent containers without component-name collisions.

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