Started to move a production implementation of the object store.

The context handle concept is being dropped, with scoped lock objects in place.
The VFS backent store now compiles.
Added missing file.

objectstore/unitTests.cpp

+#include "BackendVFS.hpp"
+#include <iostream>
+#include <memory>
+
+int main() {
+  cta::objectstore::BackendVFS bs;
+  std::auto_ptr<cta::objectstore::Backend::Parameters> params(bs.getParams());
+  std::cout << "Created a new backend store: " << params->toStr() << std::endl; 
+}
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