Implement and check SelReports

With merge request!393 SelReports are no longer created, since they need a complete re-write. They have to be re-implemented and tests added for them.

The following steps are needed for a minimal SelReport writer and are completed by !521 (merged):

• Write a test to validate that the SelReports are self-consistent as part of Allen
• Add an algorithm to calculate the amount of memory needed by the (encoded) SelReports
• Modify lines to output sufficient information about selected candidates to allow encoding of the SelReports
• Add an algorithm to encode the SelReports and copy the encoded banks to the host

The following is necessary before using the SelReports in MC production:

• Write a test to validate that the SelReports are correct using the LHCb decoder/Moore.

The SelReport writer will need to be generalized for use with more complex sequences. This will require the following (very broad) steps:

• Add support for more general candidate types (e.g. n-track vertices, ECAL clusters)
• Rewrite selections to use views that provide information about the LHCb ID container type
• Add support for parsing the LHCb ID container type and add algorithms to create LHCb ID containers.
• Add duplicate removal (e.g. if a complex sequence creates the same forward track twice)