[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/ibutton/ibutton.cpp

@@ -23,7 +23,7 @@ void AppiButton::run() {
     gpio_init(red_led_record, GpioModeOutputOpenDrain);
     gpio_init(green_led_record, GpioModeOutputOpenDrain);
 
-    api_hal_timebase_insomnia_enter();
+    api_hal_power_insomnia_enter();
     app_ready();
 
     AppiButtonEvent event;
@@ -35,9 +35,9 @@ void AppiButton::run() {
                    event.value.input.key == InputKeyBack) {
                     view_port_enabled_set(view_port, false);
                     gui_remove_view_port(gui, view_port);
-                    api_hal_timebase_insomnia_exit();
+                    api_hal_power_insomnia_exit();
 
-                    osThreadExit();
+                    return;
                 }
 
                 if(event.value.input.type == InputTypeShort &&
@@ -174,7 +174,8 @@ void AppiButton::switch_to_mode(uint8_t mode_index) {
 }
 
 // app enter function
-extern "C" void app_ibutton(void* p) {
+extern "C" int32_t app_ibutton(void* p) {
     AppiButton* app = new AppiButton();
     app->run();
+    return 0;
 }