Query filter fields should be case insensitive

When specifying a queryfilter the fields specified in that query filter should be treated as case insensitive fields. For example, if you had an entry like so:

{
  "_id" : "bobby",
  "userName" : "bob"
}

If you query that entry both of the following queries should be functionally identical and return the same results.

GET openidm/managed/user?_queryFilter=username+eq+"bob"

and

GET openidm/managed/user?_queryFilter=userName+eq+"bob"

Currently for the jdbc repo the query filter fields are case insensitive and for the DS repo the fields are case insensitive for the explicit mappings, but case sensitive for generic mappings. AM's identity endpoints are case insensitive and rest2ldap is case insensitive. To be more consistent in a platform deployment IDM should adopt case insensitivity for query filter fields. We should strive to make this change in a manner that provides no or little impact on existing customers.