FuelPHP: allow core, modules and packages to be installed

FuelPHP `1.6/develop` has started using Composer for `psr/log`, `monolog/monolog` and `fuelphp/upload`
http://fuelphp.com/blogs/2013/01/fuelphp-and-composer-revisited

This pull request makes it possible for people using `1.6/develop` to install core, modules and packages using composer. So whilst these things are not PSR compliant, starting to use composer now will hopefully make this transition much smoother and hopefully come around faster.

FuelPHP v1.x packages are prefixed with `fuel-`
FuelPHP v2.x packages are prefixed with `fuelphp-`, but FuelPHP v2 will not need to use `composer/installers`.

Here is the related pull request.
https://github.com/fuel/fuel/issues/279