Documentation update: grunt-cli is needed for fuel ISO build

requirejs is not needed anymore, it is installed locally on ISO build
nodejs should be installed from PPA since default version is too old

Closes-Bug: 1258503

Change-Id: I7f648b8991f30a3f31888a3c0d5dd386d859ca3a
Merge "Documentation update: grunt-cli is needed for fuel ISO build"