GNU Octave compatibility

Presently WebObs is using the Matlab language for most of the built-in procs. All codes are open source, written in pure Matlab core language without the need for toolboxes, and since the WebObs package contains compiled binaries, no license is required for use (see install instructions). We point out here that the use of Matlab, apart from the fact that it was an initial and relevant choice 20 years ago, still allows today a gain in execution speed of a factor up to 5 compared to similar free interpreted languages. But the last might be useful for development or even for production when the speed is not an issue. For that reason, and in order to move towards a totally free open source project, making all the codes compatible with GNU Octave has always been a long term objective.

During the transition period of development, the coding strategy remains to make Matlab optimized code (presently using R2011b), but the same code should run under Octave and produce reasonable similar results, at least without execution errors...

The last commits 269ed9e, 2b7bf73, and 77b4f2e initiated the first efforts:

• readproc is fully functional (proc and associated nodes configuration and the data import!)
• sefran3 is working with minor graphical issues (channels banner size)
• genplot is working but only with gnuplot (see OpenGL problem below)
• hypomapis working except for timeseries graphs (still OpenGL problem)
• gridmaps is functional (only with French accent issues)

In the following comment I will list the first issues (and solutions).

Originally posted by @beaudu in https://github.com/IPGP/webobs/discussions/116

Start by reviewing the built-in procedures under CODE/matlab and commits 269ed9e, 2b7bf73, and 77b4f2e, focusing on the compatibility work already described for readproc, sefran3, genplot, hypomap, and gridmaps. Done would require the Matlab procedures to run under GNU Octave without execution errors and with reasonably similar results, but the issue does not define a bounded first task.