GPS refactored (#262)

- Refactored GPS service and HAL: GPS is no longer part of the HAL configuration. You can now add configure new GPS devices from the GPS settings app.
- T-Deck adds a boot hook to check if a GPS configuration exists and adds it when the config is empty.
- Implemented the concept of ObjectFile to read/write arrays of a raw data type (e.g. struct) to disk.
- Implemented more file utils (e.g. to create all directories of a path)

Documentation/ideas.md

@@ -1,4 +1,5 @@
 # TODOs
+- rename kernel::systemEventAddListener() etc to subscribe/unsubscribe
 - Split up boot stages, so the last stage can be done from the splash screen
 - Start using non_null (either via MS GSL, or custom)
 - `hal/Configuration.h` defines C function types: Use C++ std::function instead