Homogenize docstring syntax and layout

[rhugonnet]

Right now, docstrings have a syntax and layout that is quite variable, both in the code, and after rendering in the API.
It would be nice to homogenize all of that.

1/ For the code side, maybe we could have a linter that enforces a specific layout?

2/ For the rendering side, we could decide what we think is best (including references, details about default parameters in the function description or in the parameters, or both? etc), and then open a Wiki with guidelines to write the docstring of a function consistently in the first go.

         I don't know what is the good practice, but I always remove the tab here, because in other places with different lengths (I believe e.g. when displaying the docstring from a Python console), the empty block shows up in the middle of a sentence...

Originally posted by @adehecq in #335 (comment)

[rhugonnet]

A reminder on this subject: we should remove camel-case cropGeom and use crop_geometry or similar.

[rhugonnet]

When refering to parameters in docstrings, we should probably always use ` to write for example:

"dst_ref" as dst_ref