Add single service task into the repository

Allow process admins to manually add (upload) single service task - work item handler jar. That should then add that given service task to internal service repository and automatically enable it

• uploaded jar file should be added to BC maven repo
• repository service should be updated to add new service task though mark it as unmanaged so auto updates do not apply to it
• this service task should automatically be enabled and by that allowed to be installed in projects