(DOCS)Updated dead links and reorganized the 3d printing page.

[danielwilczak101]

Updated dead links on:

• Bill of Materials
• Hardware Setup
• 3D Printing

3D printing page - Added and edited to make it more effective for users:

1. Added STL files and links to necessary components.

2. Updated tested print section. (I've hand tested these printers)

3. Added file gcode section to make it easy for users. No need to deal with configuration. Just download and print for the three printers added. This section can be expanded as the more people create these pre-saved project files.

I did not update the change log because I do not think doc updates fall under substantial changes to the code base.

Thank you,
Daniel

[danielwilczak101]

@jaybdub I was wondering if you can take a look at the pull request? We talked about it last week.