UART write example (#53)

* Rename test functions

* rewrite furi API, segfault

* make fixes in FURI, log through FURI

* add uart write example blank

* implement fuprintf instead of fopencookie

* add gif, blank page

* UART write example description

Co-authored-by: Vadim Kaushan <admin@disasm.info>

core/log.h

@@ -0,0 +1,6 @@
+#pragma once
+
+#include "furi.h"
+
+FuriRecordSubscriber* get_default_log();
+void fuprintf(FuriRecordSubscriber* f, const char * format, ...);