[skeleton] Don't use system site packages in tox environment As we changed this in cubicweb, there is a consensus that this is not the best practice so let us change it as well for skeleton.

[doc] Update "settings" pyramid documentation Document that without "bwcompat" we can use a development.ini file directly and add a dedicated section to list configuration options.

[doc] Update the "quickstart" page of pyramid documentation Again mentioning the two modes of operations and dropping references to prior implementation.