Typo.
Add a global '--sandbox-config-file' option.

Allows to specify an alternate location for the sandbox config file
(@cabal.sandbox.config@) instead of the current directory.

Usage: 'cabal --sandbox-config-file=/path/to/config build'.

Fixes #1356.
Add forgotten argument to 'warn'.
Merge pull request #1359 from hesselink/master

Small fix to get cabal-install to compile again
Print a notice when 'install -j' is used inside a sandbox.

With 'install -j' it can be a bit hard to tell where the packages are
installed. This will be reworked once we get a unified dynamic UI for 'install'.