This PR implements:

• The Preference class, which holds a single preference value and its metadata in form a sum type
• The PreferenceManager class which
  • Manages and stores all known preferences
  • Initializes them with default values
  • Path handling and creation for both Windows and POSIX
  • Loads existing values from disk
  • Provides facilities to retrieve values by their identifier
  • Allows saving of preferences back to disk
• Basic integration into OscilloscopeWindow