support for textual entity representation

[t4im]

Adding support for textual representation of components and entities would allow migrating old logging, debugging and entity management implementations like /listEntities, /showEntity or etos() which all are only aware of the old gentity_s information.

A virtual inspect method would allow components to give detailed information about state and configuration or fall back to a sensible default simply listing sub-components, handled messages and such.

A to_string method on entities (replacing etos) could give at least the Simple Classname and entity ID/Number.