Igniters, https://cwiki.apache.org/confluence/display/IGNITE/How+to+Contribute page updated.
Changes: 1) Jira process and Git process becomes part of How to Contribute <https://cwiki.apache.org/confluence/display/IGNITE/How+to+Contribute>. 2) Added 'Ticket Branch' case (only for committers). 3) Fixed minor issues. It will be nice if someone check correctness.
