(E002) prepare restructure

[ModelicaSystemCmd] add missing docstring

[OMCSession] spelling fixes

[OMCSessionCmd] add warning about depreciated class

[OMCSessionABC] remove duplicated code; see OMSessionABC

[OMSessionRunnerABC] define class

[OMCSessionZMQ] call super()__init__()

[OMCPath] fix forward dependency on OMCSessionLocal

[OMSessionException] rename from OMCSessionException

[__init__] fix imports

Author: syntron

OMPython/ModelicaSystem.py

@@ -25,7 +25,7 @@
     ModelExecutionData,
     ModelExecutionException,
 
-    OMCSessionException,
+    OMSessionException,
     OMCSessionLocal,
 
     OMPathABC,
@@ -1688,7 +1688,7 @@ def sendExpression(self, expr: str, parsed: bool = True) -> Any:
         """
         try:
             retval = self._session.sendExpression(expr=expr, parsed=parsed)
-        except OMCSessionException as ex:
+        except OMSessionException as ex:
             raise ModelicaSystemError(f"Error executing {repr(expr)}: {ex}") from ex
 
         logger.debug(f"Result of executing {repr(expr)}: {textwrap.shorten(repr(retval), width=100)}")
@@ -2829,7 +2829,9 @@ def _prepare_structure_parameters(
 
 
 class ModelicaSystemCmd(ModelExecutionCmd):
-    # TODO: docstring
+    """
+    Compatibility class; in the new version it is renamed as MOdelExecutionCmd.
+    """
 
     def __init__(
             self,