[FL-872] Furi, API-HAL, App-Loader cleanup and improvements (#334)

* Furi: replace obsolete furiac_exit with osThreadExit, drop obsolete apis and test. Rename systemd to flipper and move to separate file, cleanup. ApiHal: Rename timebase to os and move freertos hooks there, move insomnia api to power module.
* Furi: new thread helper
* Furi: cleanup thread documentation
* Flipper, AppLoader: update to use FuriThread. Update tasks signatures to match FuriThreadCallback signature.
* F4: rename API_HAL_TIMEBASE_DEBUG to API_HAL_OS_DEBUG
* Applications: rename FuriApplication to FlipperApplication, use FuriThreadCallback signature for apps.
* C++ app template sample, new exit method

applications/examples/input_dump.c

@@ -13,7 +13,7 @@ static void event_cb(const void* value, void* ctx) {
     printf("event: %02x %s\r\n", event->key, event->type ? "pressed" : "released");
 }
 
-void application_input_dump(void* p) {
+int32_t application_input_dump(void* p) {
     // open record
     PubSub* event_record = furi_record_open("input_events");
     subscribe_pubsub(event_record, event_cb, NULL);
@@ -23,4 +23,6 @@ void application_input_dump(void* p) {
     for(;;) {
         delay(100);
     }
+
+    return 0;
 }