Plugin integration

[jsilvestre]

• plugin usage is now:
  Configuration:

#./server/config.coffee
plugins: [
    'an-americano-plugin'
]

Usage:

americano = require 'americano'
americano.pluginProperty()

There is no detection of eventual collision, maybe I can add a warning message if a collision is detected (would only require to rewrite the extends function, no big deal) ?

• we can specify absolute paths for plugins (to ease plugin development/debugging)
• in the "configure" method of plugins, you can use "this" as americano instance

Before merging, I think we could discuss the plugin configuration so I can add it to the PR.
To keep things simple this is what I propose:

plugins: [
    'plugin-name': 
        'configKey1': 'config value 1'
        'configKey2': 'config value 2'
    ]

Then we could change the "configure" plugin methods by adding the options:

coffeescript
module.exports.configure = (root, app, options, callback) ->

Tell me what you think and I will add the proper changes.

[frankrousseau]

I'm ok with your change if the current way still works.

plugins: [
'plugin-name',
]

[jsilvestre]

I haven't found out a way to add plugin options without breaking backward compatibility, so I guess you can merge the PR without that change.

[jsilvestre]

I have changed loading order to avoid the following case:

• routes are loaded, they load controllers
• controllers load models
• models do a "americano.getModel" (americano-cozy example)
  => plugins are not loaded yet, getModel does not exist.