Merge pull request #150 from indikasampath2000/performance

issue fixed in trying to deliver already bufferred message
refactored slot based modifications
Merge pull request #151 from sajinidesilva/refactor2

refactored slot based modifications
Refactoring code, adding ability to handle acks in MQTT
MQTT code refactoring
Merge pull request #152 from pamod/mqtt_dev

MQTT Code Re factoring
Fix infinite loop when delivering MQTT messages.
Merge pull request #153 from akalankapagoda/InfiniteLoopFix

Fix infinite loop when delivering MQTT messages.
Fix null pointer on decrementMessageCountInSlotAndCheckToResend for topics.
debug logs modified
changed a comment
Merge pull request #155 from sajinidesilva/refactor

Refactor
Merge pull request #154 from akalankapagoda/NullOnDecrement

Fix null pointer on decrementMessageCountInSlotAndCheckToResend for topi...
issue fixed in cql range query