Update Installation model class (supporting multiple categories) and the direct category usage
Supporting multiple categories for the SENDER API
Store categories as set; add JPA annotation for collections
Adding MEMBER OF statement
Adding IN ELEMENTS() function for the multiple categories
Adding setEntityManager() hook
First test-case for the InstallationIMPL and its DAO
Adding JPA test resouses
Adding some test dependencies
Some refactoring and adding tests to query PushEndpointURLs
The categories is an 'OR'
some test overhaul work
Fixing argument typo