Project Sample Metadata - Metadata search: back-end

[deepsidhu85]

Summary

As a user I want to be able to search through metadata stored for a sample at the project and group level. This will require the use of Arel.sql

Acceptance Criteria

Add a custom search method to the group and project_namespace models (self.search) which will accept a search term as a parameter
Search at the group sample level should work on metadata fields and any other fields in the table
Search at the project sample level should work on metadata fields and any other fields in the table

[ericenns]

This issue is on hold for the moment as it is not required for our first release and the issue as defined does not have all the requirements listed.