enh(cpn): refactor edit application preferences

[elecpower]

What users will notice:

• reorganised tab contents, collapsible sections and scroll bars so content fits on screen
• renamed menus from settings to preferences to remove ambiguity with model settings

Under the covers:

• complete ui rewrite
• store code files in own directory
• eliminate monolithic code files
• change code references from settings to preferences
• extend auto widgets to support getters and setters for field values
• new auto widgets for button and file, folder, colour selection
• split OpenTx firmware settings string into separate settings fields
• housekeeping

TODO as separate PRs (as this is big enough):

• convert settings to meaningful names eg gePath holds Google Earth executable path
• refactor Firmware and Boards classes
• add models folder setting globally and per profile