Dependency as constraint vs Dependency as dependency

[fgaz]

Just opening this to keep track of how Dependency is used throughout the codebase for when we'll split it

See https://github.com/fgaz/gsoc/blob/master/2018/final-report.md#the-dependency-as-constraint-problem

• Dependency as constraint
  • configConstraints
  • Client/Outdated and packageConstraintToDependency
  • maaaybe the two lookupDependencys
• Dependency as dependency on library
  • build-depends obviously
  • setup-depends
  • DependencyMap and similar
• Dependency as "dependency" (more like... package source? hint? it's not even used..) on package
  • ProjectConfig.projectPackagesNamed

Other things to remove when doing the refactor:

• Types/Dependency.hs:
  • thisPackageVersion
  • notThisPackageVersion