Refactor app launching (#174)

- 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.

Boards/UnPhone/Source/bq24295/Bq24295.cpp

@@ -3,12 +3,15 @@
 
 #define TAG "bq24295"
 
-/** Reference: https://gitlab.com/hamishcunningham/unphonelibrary/-/blob/main/unPhone.h?ref_type=heads */
+/** Reference:
+ * https://www.ti.com/lit/ds/symlink/bq24295.pdf
+ * https://gitlab.com/hamishcunningham/unphonelibrary/-/blob/main/unPhone.h?ref_type=heads
+ */
 namespace registers {
-    static const uint8_t WATCHDOG = 0x05U; // Charge end/timer cntrl
-    static const uint8_t OPERATION_CONTROL = 0x07U; // Misc operation control
-    static const uint8_t STATUS = 0x08U; // System status
-    static const uint8_t VERSION = 0x0AU; // Vendor/part/revision status
+    static const uint8_t WATCHDOG = 0x05U; // Datasheet page 35: Charge end/timer cntrl
+    static const uint8_t OPERATION_CONTROL = 0x07U; // Datasheet page 37: Misc operation control
+    static const uint8_t STATUS = 0x08U; // Datasheet page 38: System status
+    static const uint8_t VERSION = 0x0AU; // Datasheet page 38: Vendor/part/revision status
 } // namespace registers
 
 // region Watchdog