Create a mechanism for embedders to discover required other.js version

[tonygentilcore]

@kharmabum points out that reading feature.dependencies.otherjs is too late to work for the embedder b/c that implies it has already injected some version of other.js. We should have a standard way to do this.

One possibility is replacing dependencies with something like require('other3.x'). Need to investigate the most idiomatic way to do this.

[kharmabum]

This mechanism should also return the version of the feature, words/commands, description, and any other manifesty attributes (author, source, hash, etc).