Store timestamp separately for updated issues.

Before that stored timestamp from the last processed log entry were
used to get updated issues on Jira. Experiment showed that it was not
the right thing to do. With this commit two separate files will be
created on the /tmp directory to store timestamps separately.
Update incidents one by one.

Use PUT methods for specific actions on the PagerDuty REST API.
Update incidents one by one. Reduce chance to fail. Allow incidents
to be unacknowled with the "reassign" method.
Update incidents by issue priorities.

Add "issuepriority" to the action configuration. Check issue
priority after issue status after they found by issue links.
Add required notes to the action configuration paramters on
on the README file. Update the default action configuration to
make is work by default.