Improve command line executors error messages.

- Improve descriptions of command line arguments.
- Remove meaningless default arguments.
- Add more checks to make sure command line arguments are sane.
- Add more information to some error messages.

Bug: 21161902
Change-Id: I509db5933b117b4313b6a7836274ffe091cca9d0
diff --git a/executor/xeTcpIpLink.cpp b/executor/xeTcpIpLink.cpp
index 651d199..68065c6 100644
--- a/executor/xeTcpIpLink.cpp
+++ b/executor/xeTcpIpLink.cpp
@@ -480,6 +480,7 @@
 	{
 		closeConnection();
 		m_state.setState(COMMLINKSTATE_ERROR, e.what());
+		throw;
 	}
 }