Main ucpp script can't find command scripts on some systems

Hey guys,

Great work!  I am testing on a fairly vanilla Debian Linux system, and I only had one issue - my `which` won't find bash scripts.  This means executing `ucpp init` won't work, but `ucpp-init` does.  Swapping out `which` with the built-in `sh` command `command -v` seems to work for me though.

http://stackoverflow.com/questions/592620/check-if-a-program-exists-from-a-bash-script