Remove local_tw_csv script

[siuwuncheung]

### (Requires the attention of all folks working on DMD.) This PR removes the local_tw_csv.cpp, as its functionality is included in parametric_tw_csv.cpp.

There are some additional changes in parametric_tw_csv.cpp:

• for the fixed time step case, the DMD default option is reset.
• the command lines and results are verified and added to the header.
• the instruction of the MFEM heat conduction database generation is made a little clearer.