TMDM-7455 : added junit testcase
Prevent NPE in buggy situation where field to index doesn't have a database equivalent.
TMDM-7455 Cannot search FK Record when having FK contains other FK
- If reference field type is not String, ignore the condition
TMDM-7455: "Cannot search FK Record when having FK contains other FK"

Revert for alternative in implementation.
TMDM-7455: "Cannot search FK Record when having FK contains other FK"

Alternative for implementation of fix: reuses isAssignable(...) method to check if value is assignable for field when using contains.
Merge branch 'bugfix/TMDM-7455' into feature/5.6/TMDM-7499

Conflicts:
	org.talend.mdm.core/src/com/amalto/core/query/user/UserQueryBuilder.java
Update unit test (use "or" iso. "and" in contains conditions).