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.
• fix a segmentation fault when there are multiple testing parameters (thanks @ptranq for catching it)
• 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.
• add regression tests for the capabilities

[chldkdtn]

Looks good to me!

Can you also make similar change in pylibROM as well?

Plus, can you also add regression tests on parametric_tw_csv to test local_tw feature?