Description
Following a discussion with @aloubyansky, we defined a few rules which could make it work:

• only declared compatible example codestarts (the simplest without config) could be added to an existing project
• include only the src directory and filter out files which need to be merged (config, index.html), all other sources and resources are fine..
• adding dependencies would be delegated to the parent api

Implementation ideas

1. Modify the void CodestartProjectGeneration.generateProject(final CodestartProjectDefinition projectDefinition, final Path targetDirectory) to return a result with info about the generated project (including the shared-data which contains dependencies and shared-dependencies.
2. When adding an extension to an existing project, we need to:
   • detect the "core" codestarts that it uses (buildtool, language, config, tooling)
   • detect the root package name (or use the groupId)
   • detect which added extensions contains example codestarts compatible for addition
   • generate full project
   • keep only the src dir and remove the src/main/resources/META-INF/resources/index.html and src/main/resources/application.*
   • apply them to the existing project (and log what's been added)
   • use the existing tooling to add the dependencies and test dependencies given by the result (without re-calling all this obviously)