This commit drops the 'ua_' prefix and changes the public includes
to the form `#include <open62541/server.h>` instead of the old
`#include <ua_server.h>`
Since client encryption landed into master, this was an open todo for
a long time. The multicast server example was updated to use the encryption
client.
Fixes#938
* simplify client securechannel test
* rename sleeping on simulated testing clock to UA_fakeSleep
* let the server start before calling with the client
Julius Pfrommer