Feat/MAG-36: Make CMakeLists.txt files editable

[rdsov]

This PR brings in the highly requested and anticipated feature: editable CMakeLists.txt files.

How will this work?

• Every CMakeLists.txt file will now include a custom section at the bottom, signaled by the comment "# Insert your own CMake commands after this line.".
• Any code following this line will behave like it normally would in any CMake project.
• Any code above this line still remains uneditable since that part is regenerated on the fly.
• However, you can influence this behavior by writing your own commands that act as overrides. It is planned to move as much logic as possible into variables so you can fully customize the entire process.

[linear]

MAG-36 Make CMakeLists.txt files editable