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>

wiki/fw/Application-examples.md

@@ -25,4 +25,5 @@ void application_name(void* p) {
 
 # Application examples
 
-* **[Blink](Blink-app)**
+* **[Blink](Blink-app)** show how to create app and control GPIO
+* **[UART write](UART-write)** operate with FURI pipe and print some messages