Re-integrate bootstrapping targets into version 3's makefiles

This branch re-adds the bootstrap targets into version 3's new file-based makefiles.

Todo:

• Add basic bootstrapping targets
• Investigate why the transformers library does not compile yet
• Split up the stage 1 bootstrap again due to memory issues when bootstrapping with PAKCS
• Wait for the following merge requests to get merged:
  • curry-packages/io-extra!1 (merged)
  • curry-packages/directory!1 (merged)
  • curry-packages/socket!2 (merged)
  • curry-tools!5 (merged)