refactored handling of settings '$' command out of gcode module and into settings module

nuts_bolts.c

@@ -0,0 +1,18 @@
+#include "nuts_bolts.h"
+#include <stdint.h>
+#include <stdlib.h>
+
+int read_double(char *line, uint8_t *char_counter, double *double_ptr)                  
+{
+  char *start = line + *char_counter;
+  char *end;
+  
+  *double_ptr = strtod(start, &end);
+  if(end == start) { 
+    return(0); 
+  };
+
+  *char_counter = end - line;
+  return(1);
+}
+