Create transformations for appsettings

[marknfawaz]

When migrating from a project that has web.config transformations (like debug, release, etc...), these transformations are not migrated to new appsettings files. We need to create an appSettings.TRANSFORMATION.json for each type of web.TRANSFORMATION.config:

For example, a web.config file with a Debug transformation will generate two appsetting files:
appSettings.json
appSettings.Debug.json