Fix 'opam config var list <pkg>'

Closes #1606
Fixed tput error (windows)

ref #246
Don't fail when listing available variables
Advertise additional compilers on 'opam switch list'

Closes #1575
Fix failure on some bad cl args

Closes #1644
Small package variables fix
Fix native & dynlink vars

Rename ocaml-tools-opt to ocaml-native-tools, and fix ocaml-native-dynlink for system
compilers (it now looks for `$(ocamlc -where)/dynlink.cmxa`, which should be more reliable.

Closes #1601, #1642
opam list: add option -A to list even unavailable packages, better doc

it could get misleading to pin a package and not find it with 'opam list', if uninstallable
Better behaviour with 'opam pin edit'

Edit from a temp file rather than the real one, import file from
source even if it has errors (to let the user fix them), keep
the file formatting as-is when opam has no modifications to make

Fixes  #1613 (partially)
Closes  #1650
Remove need for 'opam update' just after 'opam repo add'
make cold: switch to released OCaml 4.02.0
Merge pull request #1670 from avsm/switch-to-cold-release

make cold: switch to released OCaml 4.02.0
Merge pull request #1666 from OCamlPro/small-fixes

A bunch of fixes on beta4, mostly UI
Improve default preferences to get the latest versions for new dependencies
Merge pull request #1668 from OCamlPro/no-add-update

Remove need for 'opam update' just after 'opam repo add'
Merge pull request #1667 from OCamlPro/better-pin-edit

Better behaviour with 'opam pin edit'
config report: some more solver info
Disabling disrupting 'cache of metadata' message
Merge pull request #1677 from OCamlPro/solver-reports

Some more solver info on 'config report'
Merge pull request #1675 from rdicosmo/updatepreferences

Improve default preferences to get the latest versions for new dependencies