Ignore transitions that haven't been declared in the plugin params

In certain scenarios one may not want an issue to make a status transition after a successful build. For example, in a feature branch spanning multiple commits where the corresponding case is "In Progress", I do want TeamCity to trigger a build on each commit (and notify JIRA of the results). However, I do not want it to transition the case to "Resolved" until/unless I declare that I am done working on the issue (for example, by using a JIRA smart commit).

This patch changes the reporter behavior to attempt a status transition only if one has been declared in the plugin parameters. For example, given the following workflow configuration:
```
SUCCESS:Building-Build Passed;
FAILURE:Building-Build Failed;
```
The reporter will then only attempt to transition an issue if it has "Building" as its current status. If the issue has any other status, no transition will be attempted.