[One pull request to rule them all] Loading properties of plugin + encoding bug + passing parameter to message

[anthonyMoreira]

It's a big pull request integrating works from other pull request that has never been merged.
Issue fixed :
#13
#5
#15
#11

The main problem we had with this plugin is that it was unable to search for properties in plugins. To resolve that we did two things :

• In build mode, a special gradle task getRuntimeClasspath retrieves all of the dependency path and set a system property with all the paths. Later in I18nProcessor, we uses the different paths to check for additional properties.
• In dev mode, we use Holders.pluginManager to retrieve the properties from the plugin
  Also we saw that the current system only allowed 1 ressource to be fetched for one properties which isn't correct in case you have many plugins with properties of the same name (example : messages.properties ).
  Overrall we improved on previous pull request even if it's still kind of hackish

We upgraded the grails version to 3.2.11 due to incompatibility problem with the gradle api.

We created a plugin to automatically apply the task getRuntimeClasspath before assetCompile