Some more description of intent in symmetries.h

Former-commit-id: c5d64a7a203e5e50d9faadf0a085e5b895cf7d78

qpms/symmetries.h

@@ -6,8 +6,18 @@
  * operating on translation operators and T-matrices
  * as in tmatrices.py.
  * 
+ * At least I want:
+ * - Wigner D matrices
+ * - Basic mirror operations for T-matrices
+ * - Inversion operation for the translation matrices
+ *
  * Maybe (much later) also point and space group irrep 
  * functionality as in symmetries.py.
+ * However, I think that the group structures can be simply
+ * hard-coded/generated by a python script, then there is 
+ * no need to check the group consistency etc. at runtime.
+ *
+ * 
  */
 
 #endif // SYMMETRIES_H