Experimental MultiSlot aka General Modslot Generator (GMSG) 2.1

Changes:

• new "imgui"-based UI with many features
• generate your own standalone mods
  • select a detected template
  • automatically pack generated mods
  • custom output path
  • include template for MultiSlot compatibility
  • include dependency-resolver for automatic MultiSlot-download:
    • gmsgDownloader
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• manually generate mods
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• Settings for how stuff gets generated!
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• Utils for mod development
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Fixes:

• fixed missing mod issue
• fixed concurrency (still some improvement to go)