Update Zeppelin shell scripts

I suggest Zeppelin use a consistent shell styleguide to make code easier to read\understand and less bug-prone.
I never said zeppelin does not need it.
if you want to run zeppelin with nohup then i would user like this `nohup ./bin/zeppelin.sh& &> /dev/null`

For me `zeppelin-deamon.sh` is a deamon (**D**isk and **E**xecution **Mon**itor, by the given name of the script) so (for me) that imply a certain way of process management (must be detached) and its managed. so that why i changed the way how this script work in order to fit some "standardisation" (red had, some example of deamon script) and this deamon is waitin for an event (in the more common case `stop` witch imply kill the process)