Drop most deprecated code in cubicweb.web This includes both Python and JavaScript code. Most code has been deprecated since a very long time (versions 3.1x mostly, more than 5 years ago, and a few things until 3.24). There are still a few deprecated things, most of which are actually used within cubicweb (or in cubes we depend on for tests). I don't know what to do with these... Removed a couple of unused imports along the way. Changelog entry will come in a later changeset.

3.26 (1 February 2018)
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New features
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* For ``pyramid`` instance configuration kind, logging is not handled anymore
  by CubicWeb but should be configured through ``development.ini`` file
  following https://docs.pylonsproject.org/projects/pyramid/en/latest/narr/logging.html.

Backwards incompatible changes
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* CubicWebConfiguration method 'shared_dir' got dropped.