initial submit of type __git_file

Its a new type which can be used to tansfer important config files 
bevore and after a change to a local git repo. 

the run time point needs to be managed by the endures via require= 

We use this for example to get a revision history of all our sap profile files.
cdist makes changes via __key_value and so we have the history of every timepoint.
(for example to fulfill automatically all parts of our audits)