Add helper function to create version string

And remove all the duplicate code.

Depending on the situation prof_get_version() will return:
* 0.13.1
* 0.13.1dev
* 0.13.1dev.master.69d8c1f9

src/ui/core.c

@@ -35,10 +35,6 @@
 
 #include "config.h"
 
-#ifdef HAVE_GIT_VERSION
-#include "gitversion.h"
-#endif
-
 #include <stdlib.h>
 #include <string.h>
 #include <assert.h>