1. Added feature request for ER #46 
2. Added 2 optional attributes, commandTimeout and keepAliveInterval to
prevent MqttClient from being in a infinit wait state while performing
message publish and receive.
Changed commandTimeout and keepAliveInterval to MQTT's default value if
not specified. Externalized description of newly added parameters.
Logged message when commandTimeout happens.
Merge branch 'conglisc-321'

Conflicts:
	com.ibm.streamsx.messaging/impl/java/src/com/ibm/streamsx/messaging/mqtt/SPLDocConstants.java
	com.ibm.streamsx.messaging/info.xml