create daq boards simulator

A daq boards simulator in necessary to test the DQM and other software parts without an actual system.

• create a "packet writer", to save raw packet data (easier then to read and transmit), in lib-common/io (based on hit csv writer, but simplified). packets can be saved in txt, binary or ROOT format (or all of them, each time selected with some setting). This is needed for taking some data.
• create a daq-board-simulator executable, add it to the CMakeList.txt file

The simulator should use the DataClient class (which will need to be moved from lib-arm to lib-common), creating as many instances as simulated boards. It reads the data from a file, fills the queue of each DataClient and then sends the data to the server (usually when a queue contains more than 1000 elements). As a bonus, it can read the timestamps from the packets to send data at the right rate.