Fallback on FileContentsManager when LargeFileManager is not available
Fallback on FileContentsManager when LargeFileManager is not available

#217

mwouts/jupytext,mwouts/jupytext,mwouts/jupytext,mwouts/jupytext,mwouts/jupytext,mwouts/jupytext,mwouts/jupytext,mwouts/jupytext,mwouts/jupytext,mwouts/jupytext