install: Allow one to not retrieve kibana3 from git

My current use case is that we use images based deployment.
So kibana3 is retrieved when we build the image, but then we
deploy the images, in an environment that does not have internet.
We, hence would like to be able, to deactivate the resource as
we need.
Merge pull request #13 from enovance/manage_install

install: Allow one to not retrieve kibana3 from git