[shell] provide autocompletion for rql queries in cubicweb-ctl shell (closes #3560541)
Use the ``rql.suggestions`` component to complete user's input
- readline calls the ``complete`` method with user's input,
- the ``complete`` method asks for each known completers if
it can suggest completions for user's input.
addressbook
basket
blog
book
calendar
comment
company
email
file
folder
i18ncontent
keyword
link
mailinglist
person
tag
timeseries
vcsfile