Not compatible with native node require and webpack

[cdebost]

mr supports some features that a native node require or webpack do not. In order to eventually drop mr from montage, these features should be phased out.

• Fix module-resolution spec with bug #118 Should not expose dependencies package's require  #15 mr resolves modules differently from node. It allows loading modules relative to the package, without a relative path, e.g. require("core/foo") instead of require("../core/foo"). In Node, requires to local modules must start with ./ or ../. This difference also allows loading transitive dependencies, e.g. require("montage/collections"), which is poor practice. To minimize the impact on montage applications, we could enhance the montage deserializer to automatically convert prototype/object paths that start with ui/core/data/logic to be relative, possibly with a deprecation warning.
• mr's ReelLoader, which silently loads require("ui/foo.reel") at ui/foo.reel/foo.js, is non-standard. ReelLoader should be moved to montage proper and should log a deprecation warning, eventually requiring that components are required with the correct standard path. To avoid impacting montage serialization templates too much, the deserializer can be enhanced to interpret a prototype/object of ui/foo.reel as ui/foo.reel/foo.js.
• mappings on package.json is non-standard. This is primarily used in .info directories to avoid having many duplicate copies of montage or the parent package. This kind of thing is exactly what npm 3+'s de-duping accomplishes.
• overlay on package.json is non-standard. I don't currently know of any projects where we actually need to use overlay. The alternative is to have a single entry script that discovers the environment itself, which doesn't feel like a huge tradeoff in order to remain standard-compliant.
• browser on package.json is non-standard. It's a browserify-specific feature and mr automatically converts it to an overlay.
• directories on package.json is non-standard. It allows the user to override where mr looks for modules and unknown packages. It was actually removed from mr and montage a long time ago, but mop kept handling it. Removed handling from mop, and removed mr doc references.
• production on package.json is non-standard, but package-lock.json does have a dev property which seems to have the same purpose. I think this is only necessary due to a flaw in mop, which includes all node_modules to the final build. mop should not include devDependencies of a package in the build.
• redirects on package.json is non-standard. The only use of this I know of is montage itself, which redirects the main package's exports to montage/core/core, so that we can do <script src="./node_modules/montage/montage.js"> to bootstrap and require("montage") == require("montage/core/core").
• useScriptInjection on package.json is non-standard. Not sure about this one, when is loading via script preferable to loading via XHR?
• extraDependencies

If any of these are inaccurate, let me know or make an edit.