Use boost::program_options for devices & first version of staggered transfer shaping

**boost::program_options**
Rarely modified options like number of io threads now have default values.
To see all available options for an executable run it with '--help'.
Existing scripts have been updated to use the new format.

**staggered transfer shaping**
First implementation with the configurable offset/buffer size using std::queue.
Program option `--send-offset` controls the offset.

**etc.**
Use namespaces and adjust style according to the guidelines for FLP2EPN-distributed.