refs #8480 just created branch
refs #8480 changed nexus file holder to scope pointer

as it was locking file on failure (and probably caused memory leak)
refs #8480 Should fix the issue, but testing is needed
refs #8480 fixed unit tests compilations
refs #8480 Fixed MDEvents test
refs #8480 final changes should fix the issue
refs #8480 syntax changes for some very strict compiler
refs #8480 Added missing part of SaveMD
refs #8480 minor changes

probably unnecessary any more but just to make it equivalent to SaveMD
refs #8480 Added check if target file already exist
refs #8480 Should fix unit test failure
refs #8480 Doxygen warnings
Merge remote-tracking branch 'origin/bugfix/8480_LoadMDafterMergeMDFiles'