fbt: fixes (#1352)

* fbt: added --git-tasks; fixed typos
* fbt: fixed --extra-int-apps handling; scripts: moved storage.py & selfupdate.py to App() framework
* fbt: changed pseudo-builders to PhonyTargets with commands; added link to latest build dir as build/latest
* fbt: Restored old ep git handling
* fbt: dropped git tasks & dirlink.py
* fbt: removed extra quoting in fbt.cmd
* docs: added flash_usb to ReadMe.md

Co-authored-by: あく <alleteam@gmail.com>

site_scons/site_tools/fbt_apps.py

@@ -51,7 +51,10 @@ def generate(env):
     env.Append(
         BUILDERS={
             "ApplicationsC": Builder(
-                action=Action(build_apps_c, "${APPSCOMSTR}"),
+                action=Action(
+                    build_apps_c,
+                    "${APPSCOMSTR}",
+                ),
             ),
         }
     )