[FL-835] Factory reset. Cli refactoring. (#466)

* ApiHal: add boot flags. Internal storage: add factory reset.
* Bootloader: correct doxygen comment format.
* Cli: change cli callback signature. Applications: update API usage. Add factory_reset cli command.

firmware/targets/f5/api-hal/api-hal-boot.c

@@ -12,3 +12,10 @@ void api_hal_boot_set_mode(ApiHalBootMode mode) {
     }
 }
 
+void api_hal_boot_set_flags(ApiHalBootFlag flags) {
+    LL_RTC_BAK_SetRegister(RTC, LL_RTC_BKP_DR2, flags);
+}
+
+ApiHalBootFlag api_hal_boot_get_flags() {
+    return LL_RTC_BAK_GetRegister(RTC, LL_RTC_BKP_DR2);
+}