Feature: User Service Announcement - PASSED_BACK mode

[davidjwbbc]

Add @devbbc's work on the MBS User Service Announcements PASSED_BACK announcement mode.

An MBS User Service Announcement is passed back to the Application Provider in the response to a UserDataIngSession create/update/modify/retrieve API operation in the mbsUserServiceAnmt field if all Distribution Sessions are ACTIVE. Please note that the passing back of this field in the create and retrieve operations is not specified in TS 29.580, however since we believe this is an omission in the specification we have included it this implementation.

This completes part of issue #7

This PR also:

• Fixes an issue whereby the entryPointLocator in the ApplicationServiceDescription was using the ingest prefix rather than the distribution prefix when objDistrUri is provided in the DistributionSessionInfo.
• Fixes an issue where applicationServiceDescriptions entries were missing if no objDistrUri is provided in the DistributionSessionInfo.
• Tidies up the use of white space in the source code by expanding tabs, removing trailing spaces and making the white space used in if statements consistent.

[davidjwbbc]

Ping @devbbc

[rjb1000]

Good catches on populating the Application Service Description URLs, @davidjwbbc.