Support memory metadata

[vbmacher]

Coming from https://github.com/emustudio/emuLib/issues/78 .

Source code editor

• On all edits, it must check if that column/line contains meta-information in memory, if yes, invalidate.
• After compilation, it is responsible for showing metadata in the source code (vertical strip bar??) and link the code to debugger
  • https://github.com/emustudio/emuStudio/issues/266

Compilers

• fill in source code metadata

Memories

• Ability to add metadata by hand, and load (on startup)/store it to a file

Devices

• Ability to set metadata if a memory-mapped I/O is used