fix client_lib + add --user-function to command line

[toolslive]

ok.

[NicolasT]

Consider changing how --user-function works, by not taking an argument to the action, but reading stdin and use that as argument?

[domsj]

Right now it is indeed not suited for arbitrary binary params.

I've changed passing in of the value to arakoon --user-function bla to pass None to the user function to which you can optionally add -value foo to pass in Some "foo".

If we should later have the need for passing in binary params like this we could add another command line flag e.g. -value-from-stdin or -value-from-file <filename>.