Backends should access files safely

[DanielRJohnson]

There is a potential point of failure of backend file access in the following scenarios:

• Another user program is using a backend file (Probably not advised, but possible)
• Multiple instances of DSI are trying to read/write from the same file on a shared filesystem at the same time (Very possible)

There are a couple ways of solving this:

• Have each driver implementation be responsible for the stability of its file accesses
• Have a method somewhere higher up in the driver hierarchy that enables safety (locks, retries, etc.)
  I believe the latter is the better idea. Maybe there are other better solutions as well, these are just ideas.

[jpulidojr]

Parallel backend write support is being worked on for ingesting large subsets of files.