Rename ucioption.h to uci.h

We are going to add all UCI related
functions here, so first rename it
to a more proper name.

No functional change.

src/ucioption.cpp

@@ -26,7 +26,7 @@
 #include "misc.h"
 #include "thread.h"
 #include "tt.h"
-#include "ucioption.h"
+#include "uci.h"
 
 using std::string;