Added avsm ppa in order to install opam.
Updated ppa for ocaml 4.02 and opam 1.2/
Installing opam 1.2 from sources.
Inverted './configure' and 'make lib-ext'.
Missing sudo...
Do not need to add sagotch/opam-repo-dev repository. Pin sources instead.
--depth=1 added to git clone commands.
Added opam switch 4.02.0 instruction.