[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

core/furi.h

@@ -3,12 +3,11 @@
 #include <cmsis_os2.h>
 
 #include <furi/check.h>
-#include <furi/event.h>
 #include <furi/memmgr.h>
 #include <furi/pubsub.h>
 #include <furi/record.h>
 #include <furi/stdglue.h>
-#include <furi/value-expanders.h>
+#include <furi/thread.h>
 #include <furi/valuemutex.h>
 
 #include <api-hal/api-gpio.h>
@@ -21,7 +20,7 @@
 extern "C" {
 #endif
 
-#define furiac_exit(ptr) osThreadExit()
+void furi_init();
 
 #ifdef __cplusplus
 }