fix typos in docstring, doc and comments

[debian] remove workaround for broken sphinx/jquery combination sphinx in squeeze was updated: http://packages.qa.debian.org/s/sphinx/news/20130112T154737Z.html

[schema] mark CWDataImport as an internal type. Closes #3025536

[pkg] remove deprecated dependency on pysqlite2

Fix two crashes in db-check (closes #3024964) Also improves various debugging messages.

[rql rewrite] may_be_shared_with should consider relation's scope (closes #3024730) When a relation's scope is not the current statement, it must not be shared (instead of comparing the statement).

[rql rewrite] fix may_be_shared_with method so that it actually considers all variable infos and not only the first one

[schema/security] add __hash__ to rql expression. Closes #3013535 This is required so that when some rql expression participate to a dictionary key, only the expression is considered (consistent with comparison). This behaviour is expected in security at least, see the related bug for instance. This scramble msplanner unit tests a bit.

[rql rewrite] move some code from querier to rqlrewrite where it makes more sense. Also, make some minor cleanup/refactoring on the way and try to enhance docstrings. Relates to #3013535

Do not compute actions list in TableLayout view when display_actions attribute is unset Closes #3007281

Use the list of cubes from the filesystem when reading the schema from the filesystem Closes #3007259

[migration] when adding a cube, skip infered relations (closes #3005576) Skipped infered relations are recalculated later.

[3.17 migration] when some cube is missing, add_cube raise ConfigurationError, not ImportError. Closes #2981477

[migraction] rename_entity_type simply warn if old entity type isn't in the schema. Closes #3004069

[deprecation] fix uihelper deprecation warning, use the rtag name, not the class, so it may be copy/pasted

[test] makes fti test order-agnostic (closes #3005633)

[web/views/staticcontrollers] Make ConcatFilesHandler write to a tempfile In order to be more resistant to errors such as ENOSPC, and against different threads accessing the same static data, we: - concatenate data files to a temporary file, and rename it once we're done - delete the tempfile in case of errors - protect the creation of the cache_concat file with a lock Closes #3005547

[test] make unittest_schema.py compatible with cubicweb-file 0.14

merge 3.16.6 branch in 3.17

Added tag cubicweb-centos-version-3.16.6-1, cubicweb-debian-version-3.16.6-1, cubicweb-version-3.16.6 for changeset b4ccaf13081d

Prepare 3.16.6

[devctl] properly generate i18n messsages for cubes that uses uicfg instances (closes #2811282)

[test/devctl] add a test case for i18ncube command

Protect against crash in the `relation_possible` predicate with ambiguous relations. It was still possible to get a KeyError when using relations that are ambiguous at both ends, like (Executable, version_of, Program) & (Version, version_of, Project). Closes #3010148.