Multi file handling

[curtisy1]

Again, something to improve and implement the resx generator doesn't have

Provide a system for reading from multiple file sources and bundling them into a single namespace/file (if desired)

• Think of a reasonable grouping scheme
  • Group files in csproj or
  • Group files based on name, e.g Localization.ABC.json and Localization.DEF.json would belong together
  • Do not group at all. Every file that doesn't end in a locale is a class
• This needs to play nicely with Introduce a concept of JSON namespaces #11
• Provide an option for generating everything in a single file or multiple files