bladeRF-cli: Added -e <command> support

This option allows interactive mode commands to be executed from the
command line. Multiple -e <cmd> arguments may be provided; they will be
executed in the order they are specified.

Operations/command are performed in the following order:
    - Command line options (e.g., FPGA load, firmware flash)
    - Commands from '-e <cmd>' arguments
    - Commands from script files
    - Interactive mode commands