Members ordering should be case insensitive

[claustres]

Case insensitivity requires to use collation in MongoDB, which has multiple issues:

• each document requires a locale field for sorting to work as expected w.r.t. user's language, for now we only have it on locally registered users
• or you can create a collation-aware index but it requires your query to include it
• or you can assign a default collation when creating a collection so that indices will use it but this is an async operation not compatible with the way we setup services for now

[claustres]

Using async createCollection in model seems to work (createService being async as well), however patching existing collections seems to be hard: https://stackoverflow.com/questions/44682160/add-default-collation-to-existing-mongodb-collection.

[claustres]

We have added indices with collation on most useful languages (en/fr) and locale in find queries to ensure correct sorting.