Checkpoint fields filter StartTime
I think nektar++ can really benefit from using a "StartTime" for writing the .chk files. Say that I want to generate several .chk during a period of a vortex shedding. Right now there are two possibilities: (a) start from initial conditions=0 which will generate a lot of unnecessary .chk files because of the transient, or (b) run the simulation (without writing any .chk) and then do a restart from the .fld and write the .chk files. Because the transient will now be shorter, the number of generated unnecessary .chk files will also be smaller. In that sense, I think the Checkpoint fields filter could implement some parameter to control the time step when to start writing the chk files - exactly the same as for the aeroforces filter.
This starttime parameter should only apply to the Checkpoint filter an not to the standard checkfile writing procedure from the IO_CheckSteps parameter in the session file.
I will add the code and create a merge request.