[475131] Improve the AQL code completion

1) Introduce a new class ContentProposalWithReplacement used to provide
   additional information for a proposal. This new proposal can be used
   to replace an existing part of the expression.
2) The AQL proposal provider now returns ContentProposalWithReplacement
   objects
3) Document this new API in the release notes

Bug: 475131
Change-Id: I6f4306ee43e0a5d1eff6978ad3b8f0e70653765c
Signed-off-by: Stéphane Bégaudeau <stephane.begaudeau@obeo.fr>
20 files changed