Functions can now not only operate on parameters and maps but also on meta information

obtained from the data files. Currently the following meta information can be accessed
if available:
field in (G): B or b
energy in (keV): En or en
temperature in (K): since some data files contain a vector of temperature, they have
                    to be accessed with an index, like T0 or t0, etc.

src/include/PMusr.h

@@ -212,6 +212,16 @@ typedef std::vector<TString> PStringVector;
  */
 enum EPMusrHandleTag { kEmpty, kFit, kView };
 
+//-------------------------------------------------------------
+/**
+ * <p>keep a couple of meta data for the FUNCTIONS.
+ */
+struct PMetaData {
+  Double_t fField;  ///< field in (G)
+  Double_t fEnergy; ///< energy in (keV)
+  PDoubleVector fTemp; ///< temperature(s) in (K)
+};
+
 //-------------------------------------------------------------
 /**
  * <p>Handles the data which will be fitted, i.e. packed, background corrected, ...