Implement search for null, empty or non-exiting values

Purpose/Overview:
In some cases user will need to search for the records that do not have some values populated. For example, a librarian would like to see all records that don't have ISBN populated.

Requirements/Scope:
Search for NULL, empty or non-existing values is supported

Approach:

Acceptance criteria:

• Search for missing elements is supported
• Currently implemented search options are not affected by the new implementation
• Current performance is not affected