Fixes improper error on CryptoThread start with no message signers
Removes obsolete function connectTopology() from API

Connect topology function has been required to explicitly connect nodes into a topology. Since a few versions ago the nodes continuosly retry to connect into a topology if it has not been yet found upon the start of the node. As a result, the behavior of connectTopology can be performed automatically while starting the node.
Support for running bento node in the main application thread

* The node can be executed in caller's thread by using node::run() instead of node::start()
* It now possible to shutdown the node from node's main thread (eg. from onMessage)
* Renamed node::stop() to node::shutdown() to prevent misleading naming when exiting the node from onMessage etc.