Port save/restore services to new centralized RTI executive

[timpokorny]

Summary

Update the existing distributed save/restore services to support the new centralized RTI executive.
This must include updates about where the RTI state files are stored and how they are restored from.

NOTE: Some thought is needed on where the save/restore files shoudl be stored. Should they sit
local to the federate machine, or should each federate stream their state to the RTI for central
storage so that it can be streamed back for later restoration?

Acceptance Criteria

Once complete, Portico shall:

• use the control channel for delivery of all save and restore service calls
• store the save state files somewhere appropriate for restoration
• include RTI executive state in a new save file
• be able to confirm this functionality through the existing unit test suites
• be able to confirm this functionality through the example 1516e federate