Applications: unified entry point naming scheme, drop dead code, cleanup. (#628)

applications/ibutton/ibutton.cpp

@@ -1,7 +1,7 @@
 #include "ibutton-app.h"
 
 // app enter function
-extern "C" int32_t app_ibutton(void* p) {
+extern "C" int32_t ibutton_app(void* p) {
     iButtonApp* app = new iButtonApp();
     app->run(p);
     delete app;