Implement all internal validators

[jonathanglasmeyer]

This tracks the progress of the implementations of all internal validators, meaning those that validate the official webpack configuration properties.

Let's check an item if we have a basic, tested implementation in place.

Important

• [x] cache
• [x] context
• [x] debug
• [x] devtool
• [x] entry
• [x] module (done in #9)
• [x] output
• [x] resolve (done in #48)
• [x] resolveLoader
• [x] target
• [x] plugins ( #51 )
• [ ] externals ( #52 )
• [ ] node ( #53 )

Secondary

• [ ] amd
• [ ] bail
• [ ] devServer
• [ ] loader
• [ ] profile
• [ ] recordsInputPath
• [ ] recordsOutputPath
• [ ] recordsPath
• [x] stats (doc)

[jonathanglasmeyer]

I propose that completing all important items would satisfy an 1.0 release.

[kentcdodds]

I'm working on stats right now :-)

[jonathanglasmeyer]

Sweet. I'm tackling the three items left in Important.