External modules

[msqr1]

We should have a setting called merge (idk?) to allow "modular" modularization. Basically, it means that you can consume other modularized projects so that third-party includes have a chance to be converted to import.

Here are some things I came up:

• We will have this works with project modularized with importizer only (or some form similar to it, need to clarify). Default modularization will only work with default-modularized project, and vice-versa for transitional modularization.
• It will be a TOML-only settings, and we will use array of tables, [[externalProject]] to specify each project. Current thing(s) required from them:
  • Project input directory
  • Module interface extension