Strict model name

[frenesim]

What Currently Seed.dump will singularize all model names given in the MODELS 'option'. Here I propose to have the option to not singularize.

Why For cases where model names so not follow the convention of having the model names as singular nouns.

How Following the logic in place to send arguments in the rake task and creating a branch to not singularize the model names. Since there is 2 ways to pass in model names (MODELS and EXCLUDE_MODELS), I also perform a tiny refactor in order to have this new option crossing the already existing options.

Let me know what you think I probably cross the line with the amount of changes in this PR. We can split it or discard some changes. Cheers