Fix --help for ledctl

[mtkaczyk]

The column size should be limited to 100 chars (compatibility with terminals and kernel style).

Help should be divided into

• general_help; print modes and IBPI (backward compatibility)
• help per mode print mode specific parameters if --help is used after mode

[mtkaczyk]

Needs to be done after #119

[bkucman]

Needs to be done after https://github.com/intel/ledmon/pull/151