Make FileMetaData accumulate Lumi and Run Numbers from inputs ATLASG-1651
The new type of in-file metadata - FileMetaData - was copying metadata from the first input file and ignoring others. This made SharedWriter lose information about lumiblocks (and possibly runnumbers) from all clients except the first one. It was also printing warnings about inconsistent metadata. They will be gone now if the difference is only in lumiblocks and runnumbers.