Until now, two of the slides had images that were taken from the
Nature magazine. However, Nature does not allow redistribution of its
images! Therefore, by presenting its images in presentations and
sharing the PDF here, we were violating its copyright.

With this commit, the two images have been deleted and their slides
have been adjusted to have links to the respective paper for easy
clicking during a presentation (and showing them from Nature's own
webpage).

This issue was raised by Boud Roukema.

Until now, for the image showing a binary data analysis we were using
an image without a clear copyright statement.

In this commit, that image has been replaced by one from Wikipedia
Commans that has a sharable copyright notice.

Until now, there was no technical introduction (on what is the
necessity of Maneage in relation to Jupyter, Conda and Docker)!

While preparing the slides for the ESO "Reproducibility and Open
Science in Astronomy" meeting, I thought it will be helpful to add
such a comparison.

Given that I have now moved to CEFCA, it was necessary to add the
logos of CEFCA and Aragon government (that is funding my contract).

The place of the lecture was updated and the figure on Git branching
from the Maneage paper is also brought-in to show the capabilities.

Until now, we would immeditely jump from the part on answering the
project's questions to Git branches. But this isn't too useful for
someone who doesn't know Git! So to start the Git branching
discussion, now we first show a small image of the workflow with a
"today" printed over it. Then another one with a "tomorrow". In the
next slide we abstract them to circles with hashes!

The short version of the slides is now ready. There is a '\longformat'
macro that will significantly increase the number of slides, but not
substantially (they are just the incremental things).

Some minor modifications were also made in the long version.