[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/flipper.c

@@ -0,0 +1,26 @@
+#include "flipper.h"
+#include <applications.h>
+#include <furi.h>
+
+void flipper_init() {
+    printf("[flipper] Build date:" BUILD_DATE ". "
+           "Git Commit:" GIT_COMMIT ". "
+           "Git Branch:" GIT_BRANCH ". "
+           "Commit Number:" GIT_BRANCH_NUM "\r\n");
+
+    printf("[flipper] starting services\r\n");
+
+    for(size_t i = 0; i < FLIPPER_SERVICES_COUNT; i++) {
+        printf("[flipper] starting service %s\r\n", FLIPPER_SERVICES[i].name);
+
+        FuriThread* thread = furi_thread_alloc();
+
+        furi_thread_set_name(thread, FLIPPER_SERVICES[i].name);
+        furi_thread_set_stack_size(thread, FLIPPER_SERVICES[i].stack_size);
+        furi_thread_set_callback(thread, FLIPPER_SERVICES[i].app);
+
+        furi_thread_start(thread);
+    }
+
+    printf("[flipper] services startup complete\r\n");
+}