Fix for oracle not supporting generatedkeys method

Used a select query after inserting a queue to DB to get the queue id.
This is to avoid subtle differences in different DB vendors jdbc driver
in returning generated key for queue id.
Merge pull request #232 from a5anka/publisher_flow_control_with_disruptor

Implement publisher flow control
second time subscription null pointer exception fixed
Merge pull request #233 from sajinidesilva/serilizer-bugs

Second time subscription null pointer exception fixed
Merge pull request #234 from Asitha/oracle-issue

Fix for oracle not supporting generatedkeys method
Add missing imports
Merge pull request #235 from a5anka/flow_control

Add missing imports
Add Global limit flow control
Add documentation for Flow control related code.