[pkg] Merge python3-cubicweb-pyramid into python3-cubicweb As suggested by Denis Laxalde, we can merge python3-cubicweb-pyramid into python3-cubicweb as all other web backend in the default branch.

[pkg] Remove explicit Depends on Python packages for python3-cubicweb As suggested by Denis Laxalde, we can let pybuild generate the list of Depends from the egg requirements. The list we get is slightly less specific in terms of needed versions, but given the age of the previous ones, it's unlikely to cause issues. Also we lose python3-six from the list… which is correct as it was removed from the dependencies in 26744ad37953.

[pkg] Fix spelling mistake in doc-base abstract