Merge pull request #4 from acsaba22/review

init script cleanup.
Small fixes.
Document NSS problems.
Merge branch 'master' of github:errge/ceh
Fixed a boolean check.
Added infrastructure to install nix paths on demand (ceh_nix_install and ceh_nix_exec).
Replaced symlinks with small auto-wrappers to install stuff.
Make clibs visible to haskell interpreter.
common-functions.sh: fixed ceh_nix_install to check for installedness, not for realization.
Moved clibs needed for haskell packages into a separate profile.

So compiling GHC libs that use clibs don't pollute the user's
~/.nix-profile dir.
Small fix in ceh_nix_install.
bin/firefox added with 3 plugins working out-of-the-box: java, gtalk video, flash.
ceh_nix_instantiate_with added to make it possible to install firefox.
Small fixes around firefox.
bin/firefox: check for the target directories instead of for derivations.

So interrupted installations can continue automatically.
Use NIXPKGS_CONFIG to simplify the firefox configuration a lot.
Fix tar unpack problems in nix-init.sh

Tar extract have a problem creating symlinks in read-only directories. (It first
creates a regular file, changes the permission of the directory, and then
realizes that the file should have been a symlink, but at this point can no
longer remove it.) The --delay-directory-restore flag defers the permission
changes on the directories and fixes this issue.
Properly set up locale where locale-archive is used