Remove unnecessary long/StatusCode conversions

In preparation for a larger re-design of StatusCode clean up a few places where the code unnecessarily relies on an implicit long type-conversion. In detail:

• ObjectVector::remove: Return the index of the deleted object as documented in the base class. Before it always returned 1
• RegistryEntry: Change return type of some methods from long to StatusCode
• IODataManager: Get rid of the S_OK/S_ERROR enum alias as this relies on the actual type of the StatusCode enums
• RootDataConnection: Change return type of setCompression from long to StatusCode
• Replace a few bool-casts with isSuccess() and long-casts with getCode()

• [2017-11-13 10:42] Validation started with lhcb-gaudi-merge#295
• [2017-11-14 00:02] Automatic merge failed in lhcb-future#601
• [2017-11-14 00:03] Automatic merge failed in lhcb-future-clang#375
• [2017-11-14 00:03] Automatic merge failed in lhcb-gaudi-head#1658
• [2017-11-15 00:03] Automatic merge failed in lhcb-future#602
• [2017-11-15 00:03] Automatic merge failed in lhcb-future-clang#376
• [2017-11-15 00:04] Automatic merge failed in lhcb-gaudi-head#1659
• [2017-11-16 00:02] Validation started with lhcb-gaudi-head#1660
• [2017-11-16 00:02] Validation started with lhcb-future#603
• [2017-11-16 00:02] Validation started with lhcb-future-clang#377

added 1 commit

• 5b9f9009 - Remove implicit StatusCode casts

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changed the description

I am done with this set of changes. Would be great if someone could review this, i.e. the cases where I had to make changes to return types.

can you please re-base, as there is a merge conflict...

added 42 commits

• 5b9f9009...8395a81c - 40 commits from branch gaudi:master
• ae4e372e - Remove unnecessary long/StatusCode conversions
• ec3d2ff1 - Remove implicit StatusCode casts

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re-base done

assigned to @clemenci

added C++ framework label

changed milestone to %v30r0

added backport to v29 label

mentioned in commit a1f1375a

merged

mentioned in merge request !514 (merged)

approved this merge request

removed backport to v29 label