TestApp is a utility to be used in test suite.

Application executes each supplied command in turn. Each command get one
parameter, usually file name.

Usage:
TestApp <command1> <file1> <command2> <file2> ...

Currently supported commands:
fread <input file> - file must exist, "rb" mode
fwrite <output file> - "wb" mode

Application has one buffer so we can invoke:
TestApp fread a fwrite b
which effectively copy a file into b.

In case of error error code is returned. I would use returned error code
heavily in test suite.