Adding a metric for tracking the count of issues grouped by project and status

[Gamerick]

This adds a metric that exposes the number of issues per status, grouped by project. For example. Say we have 2 projects P1 and P2. Each project has 6 issues. P1 has 2 open, 2 in progress, and 2 resolved. P2 has all 6 issues open. We would then have four lines in the export file that look like the following:

jira_issue_status_Gauge{projectKey="P1",status="New",} 2.0 jira_issue_status_Gauge{projectKey="P1",status="In Progress",} 2.0 jira_issue_status_Gauge{projectKey="P1",status="Complete",} 2.0 jira_issue_status_Gauge{projectKey="P2",status="New",} 6.0