* Create a get_collection method similar to get_* methods for objects.
* Fix title initialization of a collection
* Remove the hack were both id and title were allowed when CDing.
That hack only worked with the canalplus module, and failed with
others like redmine (but they still showed in suggestions).
Moreover, the canalplus module now has friendlier IDs
so this is not really needed anymore.
* Allow backends to tell if a path is valid or not.
For instance, it now allows to cd in a Redmine project with no issues
in it. It also won't display "404" for invalid project IDs.
By default, we still use the unreliable method of checking there is at
least one result in iter_resources().
* Fix cd completion to work with unicode strings (all strings after an
unicode string were ignored!)
* Do not suggest '..' when completing cd in the root
refs #774
b6021d4732