Cleanups > Move common DBPS code out of server directory

[argmarco-tkd]

The DBPS code has grown somewhat organically and may need a bit of reorg.
For instance, under src/server we have the encryption_sequencer.* and some of the utils it depends on - however the sequencer is not server-only.

This task is for us to take a moment to reorganize the DBPS code into an easier-to-understand structure.

[avalerio-tkd]

#209