[Documentaton] Texture Metrics, Landscape Metrics, Sampling

[NvNorsinski]

Hello,
I think some parts of the documentation are missing for the texture metrics section.
https://force-eo.readthedocs.io/en/latest/components/higher-level/txt/index.html
Here Figure 2 is missing and in the following pages "Prequisites" and "Processing" there is no text.
The submodules Landscape Metrics and Sampling have the exact same issue.

[davidfrantz]

Thanks @NvNorsinski, I will have a look and try to provide some information, or just delete the pages if applicable.

[davidfrantz]

fyi: I deleted most of the sites that were not used. Some other things are still to do here, though.