change the way PhEDex subscriptions are made

With the disk/tape separation and a new data placement model, the Tier0 will have to make different type of subscriptions to CERN tape and T1 tape and disk. Implement these changes and also simplify the configuration to only specify the CERN site (archival_node) and the T1 tape and disk endpoints (tape_node and disk_node).
deal with case of stream injected but not in HLT menu

If we feed data for a stream that is not part of the HLT menu of if there is a stream that has not datasets defined in the HLT menu, RunConfig will already crash. The error message is misleading though, add a separate check for this and fail with a proper message.
Merge pull request #4077 from hufnagel/missing-stream

deal with case of stream injected but not in HLT menu
Merge pull request #4076 from hufnagel/phedex-subscriptions

change the way PhEDex subscriptions are made