Remove reference to leiningen.core.main; fix small typo in core_test

Implements the version of make-load-facts-form in 1dca9695, but keeps all of the subsequent 3.1.2 tweaks.

This version uses System/exit and removes the reference to leiningen.core.main in the ns. I'm falling back on [your discussion with technomancy](http://librelist.com/browser/leiningen/2013/1/1/why-can-t-i-get-at-leiningen-core-main/#32f5dcaf5b235ff87b944205da775623) in January for why use of System/exit should be OK.

This patch also addresses a small typo in core_test.