[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.

\.svn
^build$
^dist$
\.pyc$
\.pyo$
\.bak$
\.old$
\~$
\#.*?\#$
\.swp$
^doc/book/en/apidoc$
\.old$
syntax: regexp
.*/data/database/.*\.sqlite
.*/data/database/.*\.config
.*/data/database/tmpdb.*
.*/data/ldapdb/.*
^doc/html/
^doc/doctrees/
^doc/book/en/devweb/js_api/
data/pgdb/