Merge branch 'fix_multiple_omnis' into 'master'

Fix multiple omnis issue

* Fixes #71 

Co-authored by: @NickMilef <milefn@rpi.edu> 

1) DeviceClient : not a module anymore, only stores device info
and holds callbacks

2) VRPNDeviceClient : subclasses DeviceClient AND Module, to
conserve the ability to run multiple clients in parallel with
a VRPN server

3) HDAPIDeviceServer : new module that manages the HDAPIDevice
clients execution, which need to be made sequentially. Also helps
managing a unique hdScheduler.

4) HDAPIDeviceClient : lets the HDAPIDeviceServer handle the
hdScheduler. Also makes use of hdMakeCurrentDevice.

5) SimulationManager : refactor to run modules instead of
deviceservers or deviceclients

6) Sandbox : use new simulationManager API to add modules

See merge request !99