[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/u8g2_qrcode.c

@@ -13,7 +13,7 @@ void u8g2_DrawPixelSize(u8g2_t* u8g2, uint8_t x, uint8_t y, uint8_t size) {
     }
 }
 
-void u8g2_qrcode(void* p) {
+int32_t u8g2_qrcode(void* p) {
     // open record
     FuriRecordSubscriber* fb_record =
         furi_open_deprecated("u8g2_fb", false, false, NULL, NULL, NULL);
@@ -38,7 +38,7 @@ void u8g2_qrcode(void* p) {
 
     if(fb_record == NULL) {
         printf("[view_port] cannot create fb record\r\n");
-        furiac_exit(NULL);
+        return 255;
     }
 
     u8g2_t* fb = furi_take(fb_record);
@@ -63,12 +63,14 @@ void u8g2_qrcode(void* p) {
                 }
             }
         } else {
-            furiac_exit(NULL);
+            return 255;
         }
 
         furi_commit(fb_record);
 
         delay(1);
     }
+
+    return 0;
 }
 */