Adding context manager to read/write to "file.py" with optional disable

[rawe0]

It could be useful to have a context manager implemented for the read/write functions in the file.py for the cs3api4lab since it could be potentially handle large enough files where this becomes an improvement when streaming is enabled.

This would entail implementing streaming so that it can optionally be disabled since it is not supported but all applications, however it does not make sense to implement a context manager without streaming.