Two new tags under segy-format

[alfbr]

Two new tags implemented. It is location-start-time under segy-format, both under seismic-data and grid-output. It is used for manually setting the location if it differ from the standard format, similar to the other location-xx tags.

These are not exposed in the gui, but they do not break either, so the gui should produce runnable xml-files.

This is reported in CRAVA/crava#220