when writing Measurements to a CSV, format them in a machine-readable manner

i haven't tested the ones which contains commas -- hopefully the CSV
encoder deals with these :-)

crates/coremem/src/meas.rs

@@ -73,7 +73,7 @@ impl Measurement {
         &self.name
     }
 
-    pub fn str_value(&self) -> String {
+    pub fn pretty_print(&self) -> String {
         use MeasurementValue::*;
         match self.value {
             Field(v) => format!("{}{}", v, self.unit),
@@ -87,6 +87,18 @@ impl Measurement {
         }
     }
 
+    /// format the Measurement in a way that could be parseable later.
+    /// one major use case for this is in dumping the type to a CSV.
+    pub fn machine_readable(&self) -> String {
+        use MeasurementValue::*;
+        match self.value {
+            Field(v) => format!("{},{},{}", v.x(), v.y(), v.z()),
+            Float(f) => f.to_string(),
+            Int(u)   => u.to_string(),
+            Dim(v)   => format!("{},{},{}", v.x(), v.y(), v.z()),
+        }
+    }
+
     /// retrieve the float value of this measurement -- if it's of float type.
     /// useful for tests
     pub fn get_float(&self) -> Option<f32> {