[repo] Introduce a clear_caches method on the Querier class that is called from repository's clear_caches.

[repo] Consistent API for cache clearing clear_caches, reset_caches, clear_eid_caches are now all named 'clear_caches' with optional eids/etypes arguments to clear eid specific cache entry,

[repo] Extract rql cache handling to a dedicated class

[sobjects] Fix a trivial flake8 error

[repo] Drop cache clearing methods from the source interface Those are actually system source specific.

[repo] Move and rename repo._clear_planning_cache to make it clearer it's clearing the @cache of source_defs method.

[sobjects] Fix flake8 errors in services.py

[test] Rename BaseQuerierTC._access to BaseQuerierTC.admin_access so it's consistent with CubicWebTC and avoid access to a protected attribute which has been exposed by the removal of the 'session' property a few csets earlier.

[repo] Fix flake8 error

[pyramid] Add a "pyramid" instance configuration type In a new module 'cubicweb.pyramid.config' we define a "pyramid" instance configuration type. The noticeable feature of this configuration is that it manages a 'development.ini' file that gets installed in application home (along with `.conf` file). This file is templated and includes generated values for secrets of session and authtk tokens. This means that we can just call: pserve etc/cubicweb.d/<appname>/development.ini or gunicorn --paste etc/cubicweb.d/<appname>/development.ini -b :8080 just after instance creation to get a pyramid instance running without having to hack around a 'pyramid.ini' file. This patch drops 'development.ini' from skeleton and moves it in cubicweb/pyramid so that it gets installed at instance creation which is more appropriate than in cube creation. The new configuration class sets "cubicweb.bwcompat" setting to false so it is not intended to replace the "all-in-one" configuration type (which would require a bit more work). This configuration is close to the the 'repository' configuration type with just a couple of options from WebConfiguration that are needed for Pyramid (anonymous user/password plus some miscellaneous options that I'm not so sure are really needed). Note, in particular, that we do not pull CORS settings to be injected as a WSGI middleware like in wsgi_application_from_cwconfig() since I believe this should be left as an end-user responsibility and since this can be defined in a standard way in paste configuration. This configuration inherits from ServerConfiguration but registers the same appobjects as WebConfiguration. In cubicweb.web.request._CubicWebRequestBase, we guard against access to "uiprops" and "datadir_url" of the config because this new "pyramid" config does not have these (this does not make sense without bwcompat mode). At some point, we should either avoid using `cw_request`'s pyramid request attribute or make cubicweb's web request really independant of existing implementation and drop these assumptions.