[web/facet] Use an Exists node in HasRelationFacet The generated RQL now includes an EXISTS clause. For instance, one gets: :: DISTINCT Any WHERE X is CWUser, EXISTS(X in_group A) instead of: :: DISTINCT Any WHERE X is CWUser, X in_group A for a HasRelationFacet with ``rtype = 'in_group'``, which is more appropriate for testing the existence of the relation. Add a test for this facet along the way.

[MESSAGES CONTROL]
disable-msg = C0301

[VARIABLES]
# Enable / disable this checker
enable-variables = yes
additional-builtins = _, display_name

[BASIC]
required-attributes=
attr-rgx = (w|[a-z_][a-z0-9_]{2,30})
variable-rgx = (w|[a-z_][a-z0-9_]{2,30})$
argument-rgx = (w|[a-z_][a-z0-9_]{2,30})$

[TYPECHECK]
generated-members=debug,info,notice,warning,error,critical,exception