Make ModeManagerNode and ModeMonitorNode themselves lifecycle nodes?

[ralph-lange]

• Seems natural to use the same concept (i.e. runtime lifecycle) for these to nodes themselves.
• Yet, in many applications, the mode manager node will be used continuously from system start to shutdown so that there is no need for a runtime lifecycle
• On the other hand, one might think of a distributed system with multiple mode managers for subsystems which could be deactivated during runtime.
• If making the two nodes to lifecycle nodes, convenience launch files with auto-activate functionality should be provided.

[norro]

Will definitely have a look at the suggested auto-activate launch functionality, which seems to be a preconditions. Didn't yet manage to implement this, see #11.

[norro]

Since starting mode manager and mode monitor via launch files is the recommended way anyway (see system modes examples), this should be easily doable and comvenient by now.