Robotics Service Bus

Extract spread connection options into SpreadOptions

Creates a new class SpreadOptions which contains all options used to
specify the properties of a connection to the spread daemon and uses
this class instead of separate arguments or Properties instances.

This prepares to use the connection properties as keys in maps for later
sharing of connections.

refs #2196

Implement connection pooling for outgoing connections

This commit adds spread connection pooling for outgoing connection by
reusing existing connections inside SpreadFactory. The effective
activation and deactivation of the underlying connection is now
implemented via reference counting of activate and deactivate calls so
that the first user of a connection activates it and the last leaving
user effectively deactivates it.

• RefCountingSpreadWrapper: new SpreadWrapper facade implementation
  which does the reference counting for
  multiple users of an underlying
  SpreadWrapper instance.
• SpreadFactory: Cache SpreadWrapper instances based on their
  SpreadOptions to reuse them for outgoing connections
• SpreadOutConnector: Decouple the activation state from the underlying
  SpreadWrapper instance since the reference
  counting might actually leave a connection open
  after a call to deactivate

refs #2196

Make SpreadWrapper an interface

Makes SpreadWrapper and interface and moves the existing implementation
to SpreadWrapperImpl. This allows to implement facade classes, which is
necessary for the connection pooling.

• SpreadFactory: Use SpreadWrapperImpl instead of interface for new
  instances
• SpreadInPushConnector: Pass through some exceptions specified by the
  Activatable interface which previously had been
  explicitly masked by SpreadWrapperImpl
• SpreadOutConnector: likewise
• SpreadWrapper: Converted to interface
• SpreadWrapperImpl: old SpreadWrapper implementation. Also removed some
  unused methods.
• Utilities: Use SpreadWrapperImpl

refs #2196

Use the same connection for all SpreadOutConnectors

refs #2196