Standardize exit codes (mainly yarprun and RFModule)

[jgvictores]

yarpserver returns a 1 upon failing to open, and a 130 on Control-C. That's great, because it complies with http://tldp.org/LDP/abs/html/exitcodes.html. My concerns:

• yarprun: returns a 255 upon failing to open (because -1 is out of range), and a 0 on Control-C. The failure can be confusing for a .profile script that launches yarprun (in absence of a tool like icub-cluster.py in yarp, and maybe even for a script like such).
• RFModule: returns a 255 upon failing to open (because -1 is out of range), and a 0 on Control-C. A 255 would be passed as a local exit code, however, yarprun attaches a -1 (YARPRUN_ERROR) to the response Bottle... some ambiguity here.
• yarpview: returns a 0 upon failing to open, a 130 on Control-C.

[lornat75]

I am in favor of standardizing return values. My comments:

• ok for returning 1 on failure
• 0 signal success I guess
• RFModule and yarprun catch Control-C and attempt smooth shutdown, in case of success I think they should return 0, 1 otherwise.

[jgvictores]

@lornat75 Since bool return values within many functions limit the range to 2 different values, a 1 on failure and a 0 on success (obviating the originating signal) is a sound solution.