Check if file exist before using the cat command. Fixes #50.
Use boost::program_options for managing command line options of the executables.

Existing scripts in example/Tutorial3/macro have been adjusted to use the new format.
Your own scripts that use fairmq executables have to be updated.
Your own executables are not affected.
Use the `--help` option with any FairMQ executable to find out the available options.