Add support for scoped defaults in config schemas
Upgrade to underscore-plus 1.6
Accept escaped dots in config settings keys 

Fixes #3898
Add new ScopeDescriptor object
Return ScopeDescriptor objects
Update descriptor docs
ScopeDescriptor::create -> fromObject
Fix specs
Return scopes arrays from deprecated methods

backward compatibility
scopeDescriptor -> scopes

Now that we have a real ScopeDescriptor object, 
these should change back!
Oops, don’t call the method twice
Last of scopeDescriptor -> scopes from tokens
Split with the new method
Merge pull request #3907 from atom/bo-scoped-schema

Add support for scoped defaults in config schemas
Fix comments n junk
Merge pull request #3910 from atom/bo-descriptor-object

Add a ScopeDescriptor object
Cache package metadata in main package.json file
Use proper relative paths in cache
Use _atomPackage key from main metadata
Only use cache for bundled packages