Fix -Wall -Wextra warnings

[efernandez]

Continuation of #76 because I forgot to catkin clean -y and not everything was compiled with those flags. This time I cleaned everything and re-built.

I only had to fixed two types of warnings/errors:

• unused-parameter, as in Comment unused parameters #76 . I commented the parameters, but if you want I can remove them for all instances, or for specific ones.
• ignored-qualifiers, for functions/methods returning by value that had const. I removed the const for all of them because they were returning POD types. If the intend was to return a const reference instead, please let me know.

[svwilliams]

Man the compiler is picky. I need to revisit my own workspace settings. I thought I had things configured for -Wall -Wextra.

[efernandez]

Yep, @svwilliams . I indeed thought I had those flags in my catkin config, but I didn't. They're very picky, I agree, but they detect things like not returning from a non-void function, which happened to me in some other unrelated code I have in my workspace. This might be also related with the old gcc version I'm using (5.5.0), but a newer compiler will likely complain of all this issues, and in my experience if you try clang it'd be even pickier. 😃