new generic secop client

new client intended as base class for all clients

- based on Ennos secop client in nicos ([WIP] provide secop client)
- self healing connection singletons
- extension for other than TCP is foreseen (by extending new uri schemes)
- extensible name mangling
- seperate rx and tx threads supporting events
- internal cache
- extensible error handling
- callback for unhandled messages
- callback for descriptive data change
- callback for node stat change (connected, disconnected)
- a short close down and reconnect without change in descriptive data
  does not disturb the client side

works with secop-gui (change follows), planned to be used for Frappy
internal secop proxy and as a replacement for secop.client.baseclient.Client
in the nicos secop device.

-> secop/client/baseclient.py to be removed after planned changes

moved secop/client/__init__.py to secop/client/console.py because secop.client
would be the natural place to put the new base class.

Change-Id: I1a7b1f1ded2221a8f9fcdd52f9cc7414e8fbe035
Reviewed-on: https://forge.frm2.tum.de/review/c/sine2020/secop/playground/+/22218
Tested-by: JenkinsCodeReview <bjoern_pedersen@frm2.tum.de>
Reviewed-by: Markus Zolliker <markus.zolliker@psi.ch>

bin/secop-console

@@ -37,7 +37,7 @@ sys.path[0] = basepath
 
 # do not move above!
 import mlzlog
-from secop.client import ClientConsole
+from secop.client.console import ClientConsole
 
 
 def parseArgv(argv):