Added optional print_fcn argument to rfsmpp.gen_dbgcolor

This allows to redirect the colorized debug output to the Orocos RTT logger.

The `dbgcolor(...)` function has been split into `dbgcolorize(...)` that only returns the colorized string and `dbgcolor(...)` which prints the output of `dbgcolorize`.

Usage example:
```lua
fsm.dbg=rfsmpp.gen_dbgcolor("rfsm-rtt-example",
                 { STATE_ENTER=true, STATE_EXIT=true},
                 false,
                 function(...) rtt.logl('Debug', ...) end)
```