Fixes #3683: check that the regexp is valid before doing the release
Merge pull request #312 from ncharles/bug_3683/dev/validate_regex_in_search

Fixes #3683: check that the regexp is valid before doing the search
Merge branch 'branches/rudder/2.4' into branches/rudder/2.6

Conflicts:
	rudder-core/src/main/scala/com/normation/rudder/services/queries/LdapQueryProcessor.scala