When writing documentation, I realized how `onStart`/`onStop` isn't clearly communicating what it does (it could imply show/hide), so I renamed it to `onCreate` and `onDestroy`.
- Remove custom `ESP_TARGET` and use `ESP_PLATFORM` everywhere
- Add `Loader` service functionality to `tt::app::` namespace
- Make `Loader` `PubSub` usable by exposing the messages
- Add board type to crash log
- Don't show SD card in Files app when it's not mounted
- Set default SPI frequency for SD cards
- Move TT_VERSION to scope that works for sim too
- Log Tactility version and board on boot
- Rename "Yellow Board" to "CYD 2432S024C"
- Refactor the way apps work: Instead of a C interface, they are now C++ classes. The main reasoning is that attaching data to an app was cumbersome. Having different implementations for different kinds of apps was cumbersome too. (3 or 4 layers of manifest nesting for the TactilityC project)
- External apps are still written in C, but they get a createData/destroyData in their manifest, so:
- External apps now have their own manifest.
- All functions in the original AppManifest are removed and replaced by a single `createApp` function
- External apps now automatically register (each app individually!) when they run the first time. As a side-effect they become visible in the `AppList` app!
- Adapted all apps for the new interface.
- Adapted all internal logic for these changes (Gui, ViewPort, Loader, AppContext, AppInstance, etc.)
- Rewrote parts of Loader to use std::shared_ptr to make the code much safer.
- Added a refcount check for the `AppInstance` and `App` at the end of their lifecycle. Show warning if refcount is too high.
