Jira project version

This branch contains a few enhancements to the JIRA sync (SOAP and REST):

- Versions: users can now associate a project version with an SD Elements requirement. Some important points:
    - the version must exist in JIRA already; otherwise we abend
    - issues are re-opened if they have been closed and a new version is assigned
- Labels: labels are added to new issues "SD-Elements"
- RemoteLinks: JIRA 5.x issues are created with a link to an sdelements Task page
- Custom Priorities: Made small fixes with respect to custom priorities